There should really be an opportunity to donate all of your foreign change right at the gate to prevent that futile squandering on silly key chains or extremely overpriced chocolate (guilty). I would expect that every passenger has the equivalent of at least 50 cents in change - likely more in most cases - 747s accommodate roughly 500 passengers, so looking at a $250 minimum for just one flight. According to an "Aircraft Movements" statistics source, Heathrow, for example averages around 650 departures a day. Assume 75% are International and 50% are jumbo jets (thank you for humoring my guestimation here). So looking at $60K a day! I like my foreign change bowl at home, but really the sentimental value isn't worth it!
I used to scoff at all those anxious travelers that herd the gate to board as soon as possible, but today I realized, that because of their mentality, I can continue reading my book, wait until the crowd has subsided and board in a leisurely manner at the last possible instant - a strategy that wouldn't work if everyone chose it. So thank you!