AMR Corp., parent of delay-riddled American Airlines, joined other major U.S. carriers on Friday in a move to increase its ticket prices.

Passengers will have to now pay $4 to $30 more when traveling on round-trips in most domestic flights. The flight increase was lead by UAL Corp., parent of United Airlines, and matched by other carriers.

American Airlines, the Fort Worth, Texas-based airline canceled 595 flights Friday, the fourth straight day of aircraft groundings. The Federal Aviation Administration must inspect each plane before it returns to service.

The airline said 226 of its 300 MD-80 planes were back in the air Friday morning and expects 60 percent of its fleet to be back in the air by 5 p.m. Eastern time.

Passengers were left stranded after the 4 days of canceled flights, and AMR's chief executive, Gerard Arpey, said Thursday that the carrier will lose tens of millions of dollars of revenue this week.

AMR hopes to return to a full flight schedule late Saturday.

So far this year, airlines have steadily increased ticket prices in response to rising fuel costs, although higher fares haven't kept pace.

American said travelers can re-book for free and if they are stranded overnight or away from home, they will be offered free hotel accommodation.

AA has faced record fuel prices and fear of a recession, leaving analysts predicting that its parent, AMR Corp., has lost over $300 million in the first three months of the year.