Passengers on two of USA's three Christmas flights to California found a bombshell of sorts in their mailboxes Wednesday.

The bombshell was a terse letter advising the 350 students and Faculty members to make other plans for getting home.

The two affected flights--C1 to Los Angeles and C3 to San Francisco--were arranged through TWA, which has been grounded since November 5 by a strike of cabin attendants.

Flight C4 to Los Angeles, which was arranged through American Airlines, will depart as scheduled on December 20.

HSA promised a thorough search for other aircraft, but as of last night its efforts had been unsuccessful. Meanwhile, the TWA strike reportedly is far from settlement as it enters its 35th day today.

Martha R. West '74, director of HSA travel services, said she hopes to know the final status of the two flights by Monday. "I'm just as confused as anybody is at this point," she said last night.

If HSA cancels the flights, she said, charter passengers will receive a full refund before Christmas vacation. But that should be little comfort to most of them: both United and American Airlines are booked solid on almost all their California flights during the week before Christmas.