Washington, Dec. 27: The heavy rate at which the United States is losing planes and pilots over North Vietnam since it resumed heavy air raids on the North on December 18 is beginning to attract public criticism and concern. According to the Pentagon itself, a dozen heavy B-52 bombers and nearly as many fighter bombers have been lost in the space of one week alone. Hanoi on the other hand claims that it has shot down as many as 54 planes of all descriptions. The huge B-52s cost between $8 to $10 millions apiece and their losses alone accounts for over $100 millions upto date. These bombers carry a crew of six or more men and the loss of men todate totals 60 — this is one seventh of the 420 odd prisoners reported in North Vietnamese custody. Though the Pentagon maintains that this is a normal rate of attrition in raids involving 100 bombers a day, the fear is that if the raids are kept up at the current pace, the loss rate will become unconscionable. The Nixon Administration did not acknowledge the 36 hour bombing pause during Xmas until it resumed the raids yesterday. It has also said little or nothing about the purpose of the raids. Initially a White House spokesman had contended that the bombing was undertaken in order to forestall an imminent communist offensive, but the U.S. has since given up that argument. Its objective therefore seems to be to bring Hanoi back to the Paris talks and agree to a compromise that it has so far rejected. Even the most conservative eye witness accounts from Hanoi and Haiphong indicate that almost all targets of any military value in those two cities have already been reduced to rubble. A continuation of the bombing could only have the effect of making the rubble bounce — or destroy the civilian population which, according to the U.S., is not the aim it has in mind.