NEWARK - American Airlines is scrambling to explain how the company's reservation system crashed for hours on Tuesday, delaying hundreds of flights.

The airline says the system went offline in the afternoon and was resolved early in the evening.

Many passengers felt like they were not kept informed about the status of their flights. Most wondered why the normally reliable online system wasn't functioning.

American says nearly 700 flights were grounded, mostly to and from their Dallas hub. In a statement, the airline offered an apology but no details on what happened.

Officials say there could be residual delays and passengers should check the status of their flights when they arrive at the airport.