Having done the short notice travel arrangement plan (in '99 we did it after the Philly regional
), I know that it is possible. And I think we got rather lucky as we were flying out of a rather large airport (BWI in Baltimore, MD -- hub for US Air and Southwest). It just wasn't the best way of doing things. I'm sure our travel agent didn't particularly love us after those arrangements.
But it worked out so it IS possible to do travel arrangements on short notice, even if it isn't the best option.
Matt