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Exhibit 10.17 CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THE EXHIBIT BECAUSE IT IS BOTH NOT MATERIAL AND IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. OMITTED INFORMATION HAS BEEN REPLACED WITH XXXXXXXXX. Supplemental Agreement No. 15 to Purchase Agreement No. 03776 between The Boeing Company and United Airlines, Inc. Relating to Boeing Model 737 *** Aircraft THIS SUPPLEMENTAL AGREEMENT, entered into as of February 26, 2021, by and between THE BOEING COMPANY (Boeing) and UNITED AIRLINES, INC. (Customer) (SA-15); WHEREAS, the parties hereto entered into Purchase Agreement No. 3776 dated July 12, 2012, as amended and supplemented (Purchase Agreement), relating to the purchase and sale of Boeing model 737 *** aircraft (Aircraft). This Supplemental Agreement is an amendment to the Purchase Agreement; and WHEREAS, solely to conform and further amend the Purchase Agreement to reflect Customer and Boeing’s agreement regarding the following matters without duplication of any consideration being provided to Customer to (i) revise scheduled delivery of certain Aircraft; and (ii) revise certain promotional support elements; and WHEREAS, Boeing and Customer agree to (i) add the remaining 737-*** Aircraft to the Open Configuration Matters letter; and (ii) *** 737-*** Aircraft for *** 737-*** Aircraft as follows: Manufacturer Serial Number* 737-*** Aircraft Delivery Month at January 1, 2021 737-*** Aircraft Delivery Month Commencing with SA-15 to Purchase Agreement *** *** *** *** * Manufacturer Serial Numbers are subject to change NOW THEREFORE, in consideration of the mutual covenants herein contained, the parties agree to amend the Purchase Agreement as follows: 1. Table of Contents . The “Table of Contents” is deleted in its entirety and replaced with the attached “Table of Contents” (identified by “SA-15”). 2. Tables. 2.1 Table 1.1 entitled “Follow-On 737-*** Aircraft Delivery, Description, Price and ***” is deleted in its entirety and replaced with the attached Table 1.1 (identified by “SA-15”) to revise for *** 737-*** Aircraft to such table. UAL-PA-03776 SA-15, Page 1 BOEING / UNITED AIRLINES, INC. PROPRIETARY �                 !"#"$%%% &'()(*+, -./'0.(12 -.3)('4,'562 7('). *68 %%%9     :    ;       < = : !�>?@  A   A : =     =      !"#"$%%% &'()(*+, -./'0.(12 -.3)('4,'562 7('). *68 %%%9     :    ;       < = : !�>?@  A   A : =     =  BBB >BBB   = =     C   C   DC>>>C>EF  !G H   >BBB   =?      :    ; DC>>>C>EF   !G H   >BBB  >BBB   =? < = : !�>?@   >BBB   =     C   DC>>>C>EF  !   � ?     :    ; DC>>>C>EFE < = : !�>?@  A        E H E  =;       A =   =;IG   F=  F  F=         F=   !  ?<@ G    <@   <@   <A@   E J E<A@    !  K   K      ?�  LM L F=   !      ?<@   <@      !      ?�  LM LL F=   !  ?     !  K   K      ?C   DC>>>C>F  !BBB H  ? F=   !  ?   !  K   K      ?C   DC>>>C>E  �    LN? F=   !  ?     !  K   K      ?C   DC>C>EO  !P   BBB<C  @? F=   !  ?   !  K   K      ?C   DC>C>EO  !P   BBB<C  @? F=   !  ?   !  K   K      ?�         ! "# $$% �                 !"### $  ###   $% $   "& ' %    "& '  ! & ' (%   )*  ! "�  +  %,) "&        $-  ### - -  '   '  . / ### (  +! ###  $  $ !  & '  ! & '  ! . /  ### (  +! ###  $ $ !  & ' 0   $ 1 !  $     !   2 ' ### &' !   $ ###  $   �  ###   $% "&       $-  ### -  -  '   '  . / ### ( +! ###  $ $ !  & '  !& '  ! . /  ###(  +! ###  $  $ !  & ' ! & ' (0  $ 1 !  $      !   2 '### & ' !   $###  $   �  ###   $%     ! "### $  ###   $%, $   "& ' %    "& '  ! & ' (%,) "###      $     ###  $  $ !  & '  $       $  !  $     % "###      $    ###  $  $ !  & ' ! & ' ( $       $ !  $     %*) 3$ (   4 !     $  ! '!  �   $   �     ! ' $  !!0  (  ! 4 -  - 5  $  2   '  &      -  ' !! !   6  1 !!     $  !   $ !  ! -     $ $  ! $###7874&79 3 934&7  $  ! 2 ! 2 $  -  '1 �0    :;<=>? @ A>=B<C D=EF=><GH =>IJ KE;KE=<BDEL �              !" #$%&!' (! ) & *+ !,- !#.// 0  1 2  // 3 4 1 4  �5   �5  0  1 2  3 4 1 4   54    54   67578  9:5; <5  54 4=5> 85 5  ?>5 @5 @5A177 �7B   C  !" D (! ) & *+ !,- !#. %*%* &*'

�  � ��     !!"#$  %&'()*&+ ",-.! %&'()*&/ 0 %&'()*&1 02 %&'()*&3 !! 42# %&'()*&� 5/567778","#$ 0!777 -69&*& :::;);%:::<=>=?@ABCD<EC=FGBCH>=<IA<JKGL=<>C?KM::: %&'&* ;);%:::<=>=?@ABCD<EC=FGBCH>=<IA<JKGL=<>C?KM::: %&'&* ;);%:::<=>=?@ABCD<EC=FGBCH>=<IA<JKGL=<>C?KM::: %&'NO  �6 5/56777P7775/567778Q 8R  -6S6+ 5/567778Q 8R 6/ 5/567778Q 8R 61 5/567778Q 8R  -6963 5/567778Q 8R  -61T 8",UV2#!U#$ #W#LL �NO  �X 777!Y#2Z82!777X+ 777!Y#2Z82!7778 .5/567778 -69P%&'()*&T[X T[X\W#5/567778 -65T[X+ T[X\W#5/567778 -69Q- Q# 2-$$ \W# -69XX XR]!777 %&'()*&-̂0 -,̂80 Q 2$ #_̂ 606̀/55a4T̂ Xb[Qbc4Xc4--630R 8/ de �B  G *LL �f TABLE OF CONTENTS, CONTINUED LETTER AGREEMENTS UAL-PA-03776-LA-1207637R3 *** Matters UAL-PA-03776-LA-1207638R2 *** UAL-PA-03776-LA-1207640 Demonstration Flight Waiver UAL-PA-03776-LA-1207643R3 Open Matters 737-*** and 737-*** Aircraft UAL-PA-03776-LA-1207646R4 Promotional Support UAL-PA-03776-LA-1207647 Seller Purchased Equipment UAL-PA-03776-LA-1207649 Spare Parts Initial Provisioning UAL-PA-03776-LA-0000000X0 Special Matters UAL-PA-03776-LA-1208055R1 *** UAL-PA-03776-LA-1208122 *** UAL-PA-03776-LA-0000000X0 *** Matters for 737-*** Aircraft UAL-PA-03776-LA-1208157R2 *** UAL-PA-03776-LA-1208234 Privileged and Confidential Matters UAL-PA-03776-LA-1208596R2 AGTA Matters UAL-PA-03776-LA-1208238 Assignment Matters UAL-PA-03776-LA-1208869R1 Delivery *** Matters UAL-PA-03784-LA-1207869 737 Production Adjustments UAL-PA-03776-LA-1606848R2 *** Special *** Aircraft UAL-PA-03776-LA-1703685 737-*** Aircraft *** UAL-PA-03776-LA-1703743 2017 *** UAL-PA-03776-LA-1703858R1 *** Program for the 737-*** Aircraft UAL-PA-03776 TABLE OF CONTENTS SA-15, Page 2 of 3 BOEING/UNITED AIRLINES, INC. PROPRIETARY SA NUMBER SA-14 & SA-15 §3.1 SA-10 SA-15 SA-15 SA-15 §3.1 SA-10 & SA-15 §3.1 SA-7 SA-10 SA-9 SA-9 SA-13 SA-13 SA-9 SA-9 SA-9 SA-10 & SA-15 §3.1 *** Commitment for the §5.1.2 of SA-9 737-*** Aircraft UAL-PA-3776-LA-1801367 Loading of Customer Software SA-10 UAL-PA-3776-LA-1801619 Installation of Cabin Systems Equipment SA-10 UAL-PA-3776-LA-1807469 *** From *** for 737-*** Aircraft SA-11 UAL-PA-3776-LA-0000000X0 Certain Special Matters SA-14 �  �  �      !" #$%   # & '" #$(   % )& #*" #$(   '  #" #$(   ( & #$" #$*   * +,& -" #$*   ! ./, #!" #$*   -  !" #$!   0  (" #$!   $ )& (" #$-    , #(" #$-   # ./, #" #$-   % )/1 #$" #$#$   '  %$" #$#$�23345657894 :;556578 <= >? 5@;29;A BCD BEB>FGHIH$%!!* JKGL M+ NMJLXx xxX(" I % O %PQRQ QQ�D QS= Q T Table 1.1 To Purchase Agreement No. 03776 ***737-*** Aircraft Delivery, Description, Price and *** Airframe Detail Model/MTOW: 737-*** *** pounds *** Specification: *** Airframe Price Engine Base Year/*** Model/Thrust: *** *** pounds *** Formula: *** *** Engine Price Base Year/*** Airframe Price: $*** Formula: *** *** *** Features: $*** Sub-Total of Airframe and Features: $*** Airframe *** Data: Engine Price (Per Aircraft): $*** Base Year Index (ECI): *** Aircraft Basic Price (Excluding BFE/SPE): $*** Base Year Index (CPI): *** Buyer Furnished Equipment (BFE) Estimate: $*** Seller Purchased Equipment (SPE) Estimate: $*** Deposit per Aircraft: $*** # of Aircraft Delivery Date Number of Aircraft *** Factor (Airframe) Manufacturer Serial Number Actual or Nominal Delivery *** * *** Estimate *** Base Price Per A/P Advance Payment Per Aircraft (Amts. Due/Mos. Prior to Delivery): *** *** *** *** *** *** *** *** *** *** $*** $*** $*** $*** $*** Total in this Table: *** * Nominal delivery *** pursuant to Letter Agreement number UAL-PA-03776-LA-1207643R3 entitled "Open Matters 737-*** and 737-*** Aircraft", including successors thereof. Note: Serial Numbers are provided as guidance only and are subject to change. *** *** *** UAL-PA-03776 TABLE OF CONTENTS SA-15, Page 4 of 3 BOEING/UNITED AIRLINES, INC. PROPRIETARY

Table 1A To Purchase Agreement No. 03776 737-*** Aircraft Delivery, Description, Price and *** Airframe Detail Model/MTOW: 737-*** *** pounds *** Specification: *** Airframe Engine Price Base Year/*** Model/Thrust: *** *** pounds *** Formula: *** *** Engine Price Airframe Base Year/*** Price: $*** Formula: *** *** Optional Features: $*** Sub-Total of Airframe and Features: $*** Airframe *** Data: Engine Price (Per Aircraft): $*** Base Year Index (ECI): *** Aircraft Basic Price (Excluding BFE/SPE): $*** Base Year Index (CPI): *** Buyer Furnished Equipment (BFE) Estimate: $*** Seller Purchased Equipment (SPE) Estimate: $*** Deposit per Aircraft: $*** Actual or Nominal *** Per Aircraft (Amts. Delivery Due/*** Prior to *** *** * *** Estimate Delivery): Target Number Manufacturer # of *** Delivery Delivery of Factor Serial *** Base *** *** *** *** Aircraft Date Date Aircraft (Airframe) Number Price Per A/P *** *** *** *** *** *** *** *** *** *** *** *** Total: *** * Nominal delivery *** pursuant to Letter Agreement number UAL-PA-03776-LA-1207643R3 entitled "Open Matters 737-*** and 737-*** Aircraft", including successors thereof. Note: Serial Numbers above are provided as guidance only and are subject to change until delivery. *** *** *** UAL-PA-03776 TABLE OF CONTENTS SA-15, Page 5 of 3 BOEING/UNITED AIRLINES, INC. PROPRIETARY Table 1B to Purchase Agreement No. 03776 737-*** Aircraft Delivery, Description, Price and *** Airframe Detail Model/MTOW: 737-*** *** pounds *** Specification: *** Airframe Engine Price Base Year/*** Model/Thrust: *** *** pounds *** Formula: *** *** Engine Price Airframe Base Year/*** Price: $*** Formula: *** *** *** Features: $*** Sub-Total of Airframe and Features: $*** Airframe *** Data: Engine Price (Per Aircraft): $*** Base Year Index (ECI): *** # of Aircraft Target Delivery Date Number of Aircraft *** Factor (Airframe) Manufacturer Serial Number Actual or Nominal Delivery **** *** Forecast *** Estimate *** Base Price Per A/P *** Per Aircraft (Amts. Due/*** Prior to Delivery): *** *** *** *** *** *** *** *** *** *** *** $*** $*** $*** $*** $*** Total: *** * Nominal delivery *** pursuant to Letter Agreement number UAL-PA-03776-LA-1207643R3 entitled "Open Matters 737- *** and 737-*** Aircraft", including successors thereof. Note: Serial Numbers above are provided as guidance only and are subject to change until delivery. *** *** *** UAL-PA-03776 TABLE OF CONTENTS SA-15, Page 6 of 3 BOEING/UNITED AIRLINES, INC. PROPRIETARY �     !"##$#"#$ %!&'()*+ *,'-'. * )($$$+/0*12 '(#333 &#333'*' 4%4'*1+'* ( '5$6789:;<=>?@9>>A>BCD/E�   6FG>HB@D &!&'()*6I8=CGA>9D'  2&333 '*' 46?H9:9<JCD�(' '6K>C>9?@9>>A>BCD &( &(+(+'* ( ''(+(&/+&4&("' '(  .(    (+'* ( '�("' '(+'(&( &' *(('"' '!"##$#"#$ %& &L+M. '&4/E+'* ( '(   &&.'44'(#333'*' 4N333#333'*' 4 &*+&&.4333' ' *' ( ./&4&)*(&'   & +(' 'E', ' ( 2&#333 &#333 '*' 4&.( (4E(1 '*' 4-.'*&+�(*&+&&.'4 +('O(4E#333'*' 4 ''.&&� /�(*&+&&.'4#333'*' 4 ''.&&� /4' +('O(( & '&*4 +' �(*&+&&.'E/'.&&� /4' +('O(333E333P *4( /(*+&333&.'E&E(*(( 4  &.'6QGAHB<RS>RHT>9UVGBC;D3335 ' 333''5 -.'24 +('O(4E##333'*' 4 &4'(#333'*' 4 ** & ' ' E'.&E'*E(*&+&&.'4' *'*' 4E 5 -.'2(+** & ' 'N'.&&E.' '( '333E'(* O(333'   3335 -.'24#333'*' 4N'.&&4+''333!"##$#"#$ %#W2 '(  FXYZQ[\]QẐYS?Z_KZQỲaZQIb7_X7_ZŶ ?_c �                                             ��!        """ #       $""" """        #       %& '   """     �$      ()     *+*'**+*',*+*',--*+*'.*+*'�-  / /  0 """ """  � &1 '2 #   34567689:;5<6=>?876;5@%       ' *+*'"""   *+*'"""  3A6589:;5<6=>?876;5@ '        B��   1    #     B���     ) *+*'""" *+*'"""           #      %        ' *+*'"""         *+*'"""    ��C     &1 '�&1 '2 &1 'D #                3:>E7;FG?:;5<6=>?876;5:H85=GE@I��+J  !  &1%&�%& %&+    """I��2  """# """#  K   """ #   """+  ! L  +�J+      K   !  &1!�          '      !  &1!�             M N'# '-+**O'N '�-*O2+J+! '�DP) #  QRS4TUVWT4XSYZ4[\4TS]̂4T:_̀[R̀ [4SXZ[a

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