An aircraft flies 220 NM at an average planned GS of 120 kt, departing at 1200 UTC. After 70 NM it is five minutes ahead of schedule. Using the actual GS, what is revised ETA?

At 120 kt, 70 NM should take 35 minutes. Being five minutes ahead means it took 30 minutes, giving actual GS = 140 kt. Remaining distance is 150 NM, requiring about 1 hour 4 minutes. At the checkpoint it is 1230 UTC, so the revised ETA is approximately 1334, rounded to 1335 UTC. **Key takeaway:** Use observed progress to estimate actual GS and recompute only the remaining leg. **Glossary:** **Checkpoint**: A known position used to assess progress; **revised ETA**: Updated arrival estimate.