Back in the 70s we were in a bomber stream exercise flying identical routes out of Cyprus at 10 minute intervals.
We were night IMC at 430 and approaching the first time point on a celestial navigation leg. We had been given two timing options - adjust speed or do a timing trombone.
Our nav plotter decided to keep the speed up, time in hand, and lose the extra time in the trombone. Unknown to us the preceding crew elected speed adjustment.
We were only alerted as we heard him. Our IMC had been his contrails. That was scary.