I am not a medical expert and your best bet is to ask one, but I have had a bone marrow autograft (that is my own cells back after the high dose chemo therapy) so I have been a donor and a recipient.
While the AIC says a minimum of 48 hours
afterwards there is a bit more to it. Bone marrow cells can be harvested either directly from the marrow, requiring a general anaesthetic, or from the blood stream as in my case. Although the harvest itself is relatively simple, the donor usually requires some pre-treatment to ensure that there are enough free stem cells in the blood stream to make the harvest viable. For me this treatment started 7 days before the harvest and was essentially a dose of chemotherapy. The effect of which is to stimulate the bone marrow into overproduction of stem cells (to compensate for the effect of the drug) thus ensuring that there are a lot more circulating stem cells to be available for harvesting. There were then some additional drugs also designed to stimulate stem cell production. I think it would be unlikely that you would be flying during this bit.
Please don't let me put you off. As has been said, you won't be donating very frequently if ever but being available on the register might make all the difference. They are incidentally always on the lookout for male donors.
There are a number of sites available with more info but here are a couple of links:
http://www.anthonynolan.com/ndonors/matching.html
http://www.cancerbacup.org.uk/info/bone/bone-3.htm
Good Luck.