If you traveled over the Memorial Day holiday, you likely experienced jammed highways, crowded airports, and full flights.

In fact, it was the busiest Memorial Day travel period on record. But does that mean a robust summer travel season is guaranteed? Not necessarily.

Many of the people who flew over Memorial Day booked their airline tickets months earlier, when fares were considerably lower. Likewise, road-trippers made their plans before gas prices increased and chose to travel anyway.

The real indicator will be forward bookings for the July Fourth and Labor Day holidays. Right now, those bookings remain soft as many Americans appear to be holding back on future travel plans.