Bell Helicopter has been evaluating the ability of its MV-22 Osprey tiltrotor to carry the engine of an F-35 Joint Strike Fighter.

The trials, part of the company’s ongoing work to prove the Osprey as a potential successor to the Grumman C-2 Greyhound carrier onboard delivery (COD) aircraft, saw the company load a frame designed by Pratt & Whitney to carry the power section of the F135 engine loaded into the rear cabin of the Osprey.

“The container for the engine is too large to be carried in the aircraft,” said Bell CEO John Garrison on the eve of Heli-Expo 2014. He said the engine would instead be mounted in the frame, allowing the cabin of the aircraft to act as the engine’s container. It would not include the lift fan of the F-35B.

“The Marines are particularly interested in the capability,” Garrison said.

The trials were conducted using Bell’s V-22 technology demonstration aircraft in mid-February. Trials have already seen the aircraft operate from one of the Navy’s CVN carriers as well as ships and helicopter carriers from other world navies.

Bell and Boeing are optimistic about turning the long-standing Navy COD requirement into an order for the aircraft. The company hopes such an order will emerge in an as-yet-unapproved third multiyear contract beginning in 2020, which would also include more aircraft sold under the Foreign Military Sales (FMS) program.

The company delivered 41 Ospreys in 2013 and secured the second multiyear contract for 99 aircraft, including options for an additional 23. One of those options has already been exercised as an attrition replacement. The Marines now have 217 MV-22s, while the Air Force has 39 CV-22s.

Garrison also revealed that Israel was negotiating for as many as 12 MV-22 Ospreys, which is six more than was announced in the Defense Security Cooperation Agency’s notice to the U.S. Senate on Jan. 13. Japan is also looking at purchasing an additional 17 aircraft.