Defense Secretary Jim Mattis sounded optimistic Monday about the chances of repairing an unknown number of F-22s and other aircraft that were damaged when Hurricane Michael battered Tyndall Air Force Base in Florida last week.

In a gaggle with reporters on the way to Vietnam, Mattis said that based on the initial review of damaged aircraft, it “looks like all the planes are fixable.” But he cautioned that a deeper inspection of the planes — which, for maintenance or safety reasons, were not flown to different location — is necessary before the Air Force can be sure.

“I’m not ready to say it can all be fixed, but our initial review was perhaps more positive than I anticipated ... in light of the amount of damage,” Mattis said.

Mattis said that, as the storm gathered strength, Tyndall’s commander, Col. Brian Laidlaw, called his airmen back in from the three-day Columbus Day holiday weekend to try to repair as many aircraft as possible and fly them to safety. However, not all aircraft were flyable, and some — if not all — of those were damaged when their hangars were battered by the Category 4 storm.

The Air Force said over the weekend that large portions of Tyndall were heavily damaged or destroyed by the storm, including base housing. It might be weeks before the 11,000 Tyndall personnel who were ordered to evacuate before the storm will be able to return.