I had flown the leg from Batam to Jeddah on the way out—all went well—and so he flew the leg from Jeddah to Jakarta. Coming into Jakarta we're at twwenty-some thousand feet, and we get an order to descend. We're all having trouble understanding the controller. All I caught from one transmission was “descend to level” and the word “eight”. The captain said, “Eight thousand, he wants us down to eight thousand,” and dials that into the P10 panel (which really should have been my task, but he wants to run it). I dutifully read back on the radio “eight thousand”, and the controller didn't challenge that. Of course, they can't understand us any better than we can understand them, and both sides do a lot of assuming.

Now the transition level at Jakarta is 13,000 feet. Above that you use a standard altimeter setting of 1013.2 hectopascals, and altitude is referred to as “level”. Below that you use the local altimeter setting (the current barometric pressure) and altitude is referred to as “feet”. So, I'm sitting there thinking, wait a minute, if he wanted us down to to 8,000 he should have said “feet”, not “level”. Maybe what he really said was “descend to level one eight zero”. Flight levels are the altitude in thousands with the rightmost two zeroes removed.

By now I don't trust this captain any further than I can throw him, and he is a big man—ex-football player. I know he doesn't like to be challenged, and I know if I ask him him if he's sure he heard 8,000, he'll say he did, so I pick up the mic and ask the approach controller slowly and distinctly, “Confirm you want Indonesia 991 down to 8,000 feet.” This time the controller understood and immediately replied, forcefully, “Negative, negative, Indonesia 991, maintain flight level one eight zero, flight level one eight zero.”

So, problem solved; we averted a 10,000 foot altitude bust with traffic coming at us below 18,000. To the captain's credit, he thanked me for a good catch and didn't seem mad.