Replacement of Parts Except as otherwise provided herein, so long as the Airframe or Engine is subject to the Lien of this Indenture, Owner, at its own cost and expense, will, or will cause a Permitted Lessee to, at its own cost and expense, promptly replace (or cause to be replaced) all Parts which may from time to time be incorporated or installed in or attached to the Aircraft, Airframe or any Engine and which may from time to time become worn out, lost, stolen, destroyed, seized, confiscated, damaged beyond repair or permanently rendered unfit for use for any reason whatsoever. In addition, Owner may, at its own cost and expense, or may permit a Permitted Lessee at its own cost and expense to, remove (or cause to be removed) in the ordinary course of maintenance, service, repair, overhaul or testing any Parts, whether or not worn out, lost, stolen, destroyed, seized, confiscated, damaged beyond repair or permanently rendered unfit for use; provided, however, that Owner, except as otherwise provided herein, at its own cost and expense, will, or will cause a Permitted Lessee at its own cost and expense to, replace such Parts as promptly as practicable. All replacement parts shall be free and clear of all Liens, except for Permitted Liens and pooling arrangements to the extent permitted by Section 4.04(c) below (and except in the case of replacement property temporarily installed on an emergency basis) and shall be in good operating condition and have a value and utility not less than the value and utility of the Parts replaced (assuming such replaced Parts were in the condition required hereunder).