Updated from Monday, Dec. 7

CHICAGO ( TheStreet) -- United ( UAUA) on Tuesday said it was ordering 25 new planes each from Boeing ( BA) and Airbus, including the delayed Boeing "Dreamliner" 787 and Airbus A350, sources told TheStreet.

United said its 25 "firm orders" to the two manufacturers would maximize "network flexibility, cost savings and improvements for customers." It plans to discuss the order, first reported by TheStreet Monday night, in a 10 a.m. conference call.

People familiar with the order on Monday confirmed to TheStreet that the order would include the Boeing Dreamliner and Airbus A350, which would represent a major boost for each of the two manufacturers, since significant delays have hampered each aircraft's development. Spokesmen for Airbus and Boeing and United declined to comment on TheStreet's report Monday.

The Dreamliner is more than two years behind schedule, although Boeing has said the first one will fly by the end of 2009. Airbus, meanwhile, is expected to start to build the first A350 early next year: it is not expected to be available for at least five years.

United would become the last of the major U.S. airlines to place an order for one of the new composite airplanes. US Airways ( LCC) and Hawaiian Airlines ( HA) have ordered A350s, while American ( AMR), Continental ( CAL) and Delta ( DAL) have ordered the 787.

On United's second-quarter earnings call, Chief Financial Officer Kathryn Mikells said the carrier expected to announce an aircraft order before the end of the year "that would be committing the company to a long-term fleet replacement strategy." She said the aircraft "would not come for some number of years into the future."

-- Written by Ted Reed in Charlotte, N.C. .