If you're not entirely sure if you're allowed to pack your favorite can of hairspray, your teenager's hoverboard, or that cellphone to which your companion seems to be surgically attached, you're in good company. 

Travelers are finding it increasingly difficult to remember all of the items that aren't allowed on an aircraft. This isn't a new problem — they've been confused since shortly after 9/11 when eager security screeners started confiscating nail clippers — but the problem seems to be getting worse. 

"The unfortunate truth is that regardless of the steps airlines take to make passengers aware of restrictions, there always will be some passengers who remain unaware," says Barry Alexander, an aviation attorney at the Philadelphia-based law firm Schnader Harrison Segal & Lewis. "Some of those passengers likely will blame the airlines. 

Where to find out about the rules

When you're flying domestically, there are at least three places to check before you fly.

• The Federal Aviation Administration. The FAA publishes a Pack Safe guide FAA that focuses mostly on hazardous materials such explosives, flammable liquids and radioactive materials. These items are not allowed on any commercial flight, so consider this the most authoritative list.

• The Transportation Security Administration. A far more extensive list of banned items is published by the TSA on its site TSA. But that list can change and, as the TSA notes, the final decision on whether something is allowed onboard or not rests with the TSA screener at the checkpoint. Also, don't forget to check that liquid rule: TSA.

• Your airline. Airlines have their own list of items that are and aren't allowed on a plane. Their lists usually match the government's lists, but not always. See Delta Air Lines' website, for example: Delta Airlines.