American production, black & white (I believe), so guessing mid-50s to early 60s. Caught only last ~15-20 minutes of movie (about 45-50 years ago) on TV, so can’t help with other scene(s). Likely a “B” movie, but unsure. Actor unknown. Climactic scene(s) included: an activated or damaged atom bomb (capsule shaped) sitting on or near runway at base or airport, then being chained to either a bomber or helicopter by hero pilot who sacrifices self to radiation exposure and flies bomb away from city (over ocean?). Bomb explodes, killing hero pilot. Disaster averted.
“Panic in the City” (1968)?
At the end of the movie the hero American agent manages to locate the house with the bomb inside. A US Coast Guard Sikorsky HH-52A Seaguard (Sikorsky S-62) arrives at the scene and lands in front of the house. The hero drags the bomb out of the house and attaches it to the belly of the helicopter. He then flies the helicopter with its lethal underslung cargo out to the ocean. The bomb goes off, the city is saved, but the hero sacrifices himself in the process.