Maybe you were thinking of B-36s because there were only 2 B-70 Valkyries built and one crashed.
Although in the 60’s I don’t think many B-36s were still flying.
I knew an old pilot who flew the B-36s. He told me that was the reason that bases like Eglin had the 14,000 foot runways.
He told me had flown every plane in the Air Force from WWII until the 70s except the B-17 and that included the U-2 and SR-71.
After he retired, he got a job at Ft. Rucker training army pilots. He said when the interviewer asked if he was certified in two engine planed, he told him he was certified for 10 engines (the B-36).
Nostalgia: If you looked generally south from Mt. lemon it was like looking into a mirror at about a 45 degree angle.