Made it to the gate with that overstuffed carry-on bag? Not so fast! These days, airlines are cracking down on both checked bags and carry-on luggage. Those "size wise" bins that are stationed throughout airports and seem to fit only a shoebox are being reinforced as airlines seek to speed up boarding time with fewer carry-ons that can slow down the process. Some airlines go so far as to use scales at the gate to ensure that no bag is heavier than their specified guidelines.

Most airlines do not charge a fee if they check your bag at the gate, but some, like Air Asia, do. And more annoying than the potential fee is the idea of being separated from their carry-ons, often packed with electronics, medications, and other valuable items that travelers do not want out of their sight. Remember to keep valuable items close to you in case a gate agent insists that you check your bag in a hurry.

Gate agents tell us this is all meant to discourage people trying to sneak massive bags past check-in counters. Delta Air Lines, like many European airlines, instituted a policy where all cabin baggage on international flights should have a red tag indicating that an agent has approved it before passing security. This This is the result of some passengers approaching the counter to check in with one bag while their friends stand elsewhere with multiple bags that the passenger intends to carry onboard.

This handy chart provides the latest information on airlines' policies for cabin baggage, along with comments on specific airline nuances.