Flying on a plane before shabbos is not like embarking on a boat regardless of the reasoning (I remember 4 offhand):
- The sea-sickness will breach your kavod shabbos: Anyone who has been on a medium size boat in the ocean without dramamine knows that this is no comparison to flying on a plane which is pretty smooth.
- The crew is doing melacha for you: Does not apply if most of the passengers are not Jewish.
- You will be forced to do melacha in a dangerous situation: No weather satellites back then, so it was common to run into a storm and have to violate shabbos. Not true with a plane ride. Besides, what are you going to do?
- You may not travel beyond the techum on shabbos: If you are above 10 tefachim before shabbos, you are not subject to techum.
(At some point I'll bring sources and other possible issues that don't apply.)
I asked my Rav regarding my neighbor who travels to Asia and Australia. He said that although the Chazon Ish could do it, we would have a problem. The Chazon Ish would keep Friday and Friday night until he got to the Asian coast, then it would be Saturday night. But since there was never a clear ruling on the dateline, once we cross the international dateline (but before the Chazon Ish's dateline) we would be in doubt about our obligations. That night, are we obligated in kiddush or havdala? It might be possible to work it out a situation where there are no doubts, but I haven't tried.
I hope it is clear that you must keep the "little" shabbos and make havdala. Of course you'll have to ask someone to stand in front of the lavatory for you since the light will go on if you slide the lock!