US Airways has found yet another investor willing to lift it out of bankruptcy and support its planned merger with America West Airlines.

Wellington Management Company, a Boston investment fund with $470 billion in assets under management, agreed recently to provide the Arlington, Va.-based airline with an additional $150 million, according to new documents filed with the U.S. Bankruptcy Court in Alexandria, Va.

Wellington, founded in 1928, joins four other investors committed to $350 million in new equity capital, including Air Canada, Air Wisconsin Airlines and two investment funds.

Unlike some of the other new investors, however, Wellington will not have a spot on the new board of directors of the merged US Airways-America West, nor will it be entitled to a break-up fee if the union falls apart, according to court documents.