С появлением варианта 737 Higher Gross Weight первого поколения и 737-400 (на снимке) фирма "Boeing" вышла с самолетом 737 на рынок среднемагистральных авиалайнеров. Объемы продаж самолетов 737-300/-400/-500 с двигателями CFM56 значительно превзошли продажи самолетов 737-100/-200.
Air UK Leisure began operating its first 737-400 from London Stansted Airport on 27 October 1988, with a series of return flights to Faro, Portugal, on behalf of tour operator Unijet. Leased from GPA, this and two to follow are operating at the intermediate weight of 143,000 lb (64 865 kg).
19 февраля 1988г.: совершил полет Boeing 737, Series 400, способный перевозить до 168 пассажиров.
Компания "Piedmont Airlines" из Уинстона-Салема (США) получила свой первый 737-400 в сентябре 1988 года. Самолеты компании имели салон на 146 мест.
Piedmont Airlines became the first operator to take delivery of the 737-400, on 15 September 1988, and flew the first revenue service on 1 October. Following the practice of its parent company US Air, Piedmont now has its aircraft in a polished natural metal finish.
The Boeing 737-400 was certificated in 535 hours flown by two aircraft in six months, with Type Approval confirmed by the FAA on 2 September 1988.
Air UK leased three -400s from GPA to allow it to become the second airline to put the latest Boeing into service.
First of the stretched Boeing 737-400s into the air, on 19 February 1988, N73700 shown here was in Boeing's house livery and bore on its forward fuselage the logos of the nine companies that had ordered the variant by that date.
Commonality between the 737-400 and the two shorter variants, the -300 and -500, which are also now in production, is a significant setting point for Boeing and was sited, for example, by British Airways for its October 1988 decision to buy a fleet of 24 (plus 11 options) new 737s that will probably include all three versions. Flight deck commonality allows pilots with a single rating to fly all three types
Common interior features reduce spares holdings, simplify maintenance and shorten training periods for cabin crews.
To fly within the next few months, the 737-500 (here depicted in the colours of Aer Lingus) is scheduled to enter commercial service in March 1990.