Different airlines and airports have different standards for how they process luggage. Although many new rules have been put into effect due to recent world events, some things remain the same. All luggage, regardless of its owner, size, shape or seeming safety is subject to search. This rule is more of a deterrent than anything else. If luggage is more likely to be searched without cause, it is less likely that possibly offensive or dangerous items might be placed in the luggage for travel. Furthermore, airlines usually have a policy that they can refuse luggage, without warning, for a variety of reasons including but not limited to size, weight, character or condition.
The condition can be particularly important. Well made luggage that looks sturdy will have a better chance of making it through a flight than luggage in a questionable condition. They will also refuse luggage if the inclusion of the luggage would harm or inconvenience other paying customers aboard the flight. There is usually a luggage cut-off time. This is the time at which luggage is no longer allowed onto the aircraft or into checking. This is because the luggage must be loaded within a certain period...