Originally Posted by wetrat0

If you leave LGA on time you'll be fine. For starters, 39 minutes is tons of time if you don't have to change piers (max walk within a pier is like 5 minutes). While it's a bit tight if you have to change from B/C pier to C pier, because you have to take a bus, the LGA shuttle schedules are padded-- they block 1:20 for a 0:45 flight-- and plenty of people are making these connections everyday. Again, basically everything depends on how things are going at LGA and whether your departure is late. Personally, if I was doing this, depending on the time of day I would be making an effort to standby for an earlier LGA-DCA flight (they run as often as every hour).