Many children have gone back to school in the U.S., and the days are getting shorter, but there is still one more excuse to use the swimsuits and beach towels before packing them up: Labor Day. Airports, highways, beaches and theme parks are expected to be packed for the long holiday weekend as a lot Americans mark the unofficial end of summer the same way they celebrated the season’s unofficial start: by traveling. The Transportation Security Administration anticipates screening more than 17 million people between Thursday and next Wednesday — a record for the Labor Day period. AAA says bookings for domestic travel are running 9% higher than last year for the holiday weekend, while international trips are down 4%. Motorists are getting a break on gasoline compared with last year. The nationwide average was recently $3.37 per gallon, compared to $3.80 a year ago, according to AAA spokeswoman Aixa Diaz. If you plan to start your drive on the Thursday or Friday before Labor Day, you will be sharing the road with commuters. You might want to leave before morning rush hour or even in the evening to avoid jams. Transportation-data provider INRIX says the worst time to travel by car on Thursday will be between 1 p.m. and 7:30 p.m., and on Friday between 2 p.m. and 6 p.m. That flips on Saturday, when you'll want to avoid driving between 8 a.m. and 11 a.m. For the return trip, pretty much all day Monday — from 11 a.m. to 8 p.m. — will be a slog, according to INRIX.