The Marine Corps' top general says the much-maligned F-35 joint strike fighter will likely see combat early next year.

"We're going to start to see that airplane deploy here overseas after the first of the year," Marine Commandant Gen. Robert Neller told an audience at the Center for Strategic and International Studies in Washington on Tuesday.

Neller says the long delay in delivery of the Lockheed Martin F-35 was largely responsible for current shortfalls in aviation readiness, as the Corps has had to keep older planes flying longer than planned.

"The F-35 is going to replace three model type series, the Harrier, the Hornet, and the Prowler," Neller said. "We thought we were going to get that airplane a little bit earlier, but we didn't."

Neller says a second squadron of F-35Bs has been stood up, and that will make deployment into combat possible.

This month, Marine AV-8B Harrier jump jets were used to attack Islamic State targets in Syria.

The Harrier has been in the Marine Corps inventory for 30 years, and is scheduled to be phased out as its vertical/short-take-off-and-landing mission is taken over by the VSTOL version of the F-35.

Neller said Marine Corps aviation is coming out of a nosedive in readiness, as the Corps has gotten better at finding spare parts, and cycling aircraft though maintenance depots.

"We're starting to see now slow, steady improvement," Neller said. "I'm not going to spike the ball because we've got to get more airplanes on the ramps so our air crews can fly more hours."

Neller said his biggest problem is keeping older CH-53 helicopters flying, while the Marine Corps awaits delivery of a new model that's still in testing.

He said the problem was compounded by a big mistake of maintaining forward-deployed helicopters in theater instead of bringing them back for full overhauls between deployments.

"We should have done that and they would have been in a better state than they are now," Neller admitted. "So now we're having to do that and — but it's going to take some time."