With most of its aviation funds tied up in the V-22 Osprey program (and the expensive upgrades to the UH-1 and AH-1 fleets), the Marines are looking for ways to keep their CH-53 and CH-46 helicopters flying until 2025. As they stand, these airframes will not last that long; they will reach their maximum service lives by 2010-2015. The Marines plan to upgrade 140 of their 160 CH-53Es, converting the last two squadrons to V-22s. The CH-53E upgrade is known as "tube and tail" since it replaces or strengthens the structural members in the cabin and tail sections. While no money has been allocated, the Marines are hoping to get the funds for a program to develop the refit from 2004-2008, with conversion starting in 2011 at a rate of 15 aircraft per year. The problem with the CH-46 fleet is the engines, which have grown increasingly unreliable. Mean time between repairs has fallen from 900 hours a few years ago to only 370. The Marines know that they will have to improve this score in order to keep the CH-46s flying until 2012, when they will start being replaced by MV-22s.--Stephen V Cole