US airline owner AMR Corp., parent of bankrupt American Airlines Inc., has asked for more time to file a restructuring business plan, court papers indicate. Creditor committees have joined the petition for what would be the fifth extension for filing a plan, The Wall Street Journal reported Saturday. The extension would give the company an additional 20 days to file a plan, which would push the current deadline to April 1. Concurrently, it is expected that AA and US Airways would soon announce a decision on whether they would join forces. AA has been studying the option of merging with US Airways but details on talks between the two companies have been shielded from the public by a non-disclosure agreement signed by both parties last August. Creditor committees and union groups are a party to the discussions but the public has largely been kept out of the loop, The Dallas Morning News said.