As the fifth-generation F-35 is readied for operational use, the U.S. Air Force is looking for ways for the bird to communicate with younger fourth generation planes.

The Air Force is currently planning a request for proposal for “5th to 4th” capabilities, according to Aviation Week.

The biggest concern from the Air Force is to find a 5th to 4th communications system that will not jeopardize the stealthiness of any aircraft. Aviation Week reported that one of the major issues is “how to allow for the F-22 and F-35 to communicate without using Link 16 alone, which would compromise their stealthy operations.”

Though both are manufactured by Lockheed Martin to meet Air Force needs, they were designed in different eras. F-22s can essentially only “talk” to other F-22s through a dedicated, low-probability-of-detection/low-probability-of-intercept system. The F-35, by contrast, uses the Multi-function Advanced Datalink (MADL) system, which employs a different waveform; the F-35 is slated for its Air Force operational debut as early as August 2016.

The Air Force is exploring a few different options, but nothing concrete has been established as RFP is readied.