LONDON (AP) _ British Aerospace announced Tuesday it has reached an agreement to sell its entire output of ''quiet jet'' freight planes over the next five years to the Australian TNT freight group in a deal worth $1.5 billion.

British Aerospace called the agreement, at 942 million British pounds, ''a commitment -- not a firm order.''

It gives TNT, which has been seeking to expand its overnight freight network, as many as it wants of the 72 British Aerospace 146 Quiet Trader freighter aircraft scheduled to be built between now and 1992 - with the remainder going to its associated company Ansett Worldwide.

Ansett is to sell the left-over planes to other companies in a joint agreement with British Aerospace.

The agreement was hailed by British Aerospace as a solid endorsement of the 146, which, in passenger as well as freight versions, is widely accepted to be one of the world's quietest jets.

The four-engined 146 is the largest civil airliner manufactured by the British Aerospace, which is a major partner in the European Airbus consortium.

It can carry up to 100 passengers and is specially suited to small airports with short runways.

Nearly 100 of the 146s already have been sold worldwide, mostly to various American airlines.