UPDATE 5-American says TPG could invest in struggling JAL

* TPG may join American in investment in JAL-AMR CFO

* State bank to offer $1.1 bln credit line-sources

* 3 private banks to offer Y25 bln in loans to JAL - sources

* JAL may post 90 bln yen first-half operating loss - Nikkei

* Shares rise 4.8 pct in flat mkt; down almost 50 pct in 2009 (Adds detail on American estimate in paragraph 11)

By Nathan Layne and Nobuhiro Kubo

TOKYO, Nov 11 (Reuters) - Private equity firm TPG could partner with American Airlines on a minority investment in Japan Airlines (9205.T) to prevent its defection to a rival airline group, the chief financial officer of American parent AMR Corp (AMR.N) said.

The emergence of TPG [TPG.UL] as a potential investor comes as the loss-making Japan Airlines seeks its fourth state bailout since 2001, saddled with $15 billion in debt, a massive pension deficit and dozens of unprofitable routes.

The Japanese government pledged on Tuesday to enlist a state bank to offer bridge loans to prevent the airline from running short of cash and said it may introduce legislation to cut a pension shortfall that hit $3.7 billion in March. [ID:nT287070]

Even as it struggles to avoid bankruptcy, JAL is being wooed separately by American Airlines and Delta Air Lines, which are keen to gain access to JAL's network in Asia and a stronger foothold in Japan. JAL is Asia's largest carrier by revenues.

AMR's Thomas Horton said TPG, which helped fund Continental Airlines emergence from bankruptcy in 1993 and backed a failed takeover attempt for Australia's Qantas Airways (QAN.AX) in 2007, has agreed to potentially invest in JAL as part of any deal with American Airlines.

"As appropriate and if it were welcomed by Japan Airlines and the government of Japan, TPG could also be part of a comprehensive recovery plan," Horton told reporters in Tokyo.

"They have been active in the airline space over the years."

A spokesman for TPG in Tokyo declined to comment.

American partners JAL in the Oneworld alliance, which pools frequent flyer miles and feeds passengers between members, and is keen to block it from joining Delta in the rival SkyTeam group.

American has argued that JAL and Delta would have difficulty clearing regulatory hurdles if they sought antitrust immunity for closer business ties because the alliance would give SkyTeam control of 60 percent of air traffic between Japan and the U.S.