I saw something similar at LAX International. Passanger jets lined up to land. I was Standing outside the Melody Bar directly under the landing aproach trajectory. Four and sometimes five airliners coming in. About 30 or 40 seconds apart. Los Angeles is a very big and busy airport.
The jets would be only 100 metres above me as they flew over. I stood watching for at least 15 minutes. The spacing intervals never changed more than a few seconds. It was like military precision.
Cheers