Effective November 1, Continental's maximum allowable carry-on size will shrink from 51 linear inches (the combined length, width, and height) to 45 linear inches. According to Continental, this move will align Continental's restrictions with those of its SkyTeam partners, which include Delta, Northwest, and Air France.
A Continental spokeswoman told BusinessWeek the carry-on downsizing has nothing at all to do with the airline's recent decision to implement a $15 checked-bag fee, but I'm not buying it. Checked-bag fees have led people to try traveling only with a carry-on, which inevitably results in a few folks stretching the limits of what an overhead bin can hold. Reducing the allowable carry-on size will surely free up some space in those bins—which, mind you, is not a bad thing—though it will make it a little harder to travel sans checked baggage.
Here's Continental's carry-on policy, updated to reflect the change.