This was a new one for us. My wife and I boarded our BA flight from YYZ-LHR two weeks ago, on a very full B777-200. Flight was ready to go on time, but just as departure from the gate should have started, the captain announced that we would be a few minutes late departing because the lavatory's holding tanks were frozen solid, and it would take a while to be able to drain them.

So we sat on this very full (in more ways then one) aircraft for about 45 minutes while the ground crew tried to defrost the holding tanks sufficiently to have them emptied and allow us to get airborne.

While I understand that those tanks have to be drained for long flights at each turnaround point, I didn't think that they froze, considering their, uhm, contents. Remembering BA 38 and it's engines off landing at LHR because of frozen jet fuel clogging the fuel lines, but are frozen lav tanks a common occurrence? It had snowed all day on the day we left for London in the late afternoon, and I'm guessing that our aircraft had only been on the ground two, possibly three hours on arrival from LHR for our return flight there.

The flight deck was able make up most of the delay with the help of a favourable tailwind, having us arrive at LHR only about fifteen minutes late.

bj-21.