Service Bulletin 52-37 was issued by Douglas on July 3rd 1972, three weeks after the Windsor incident in which the rear cargo door blew off and caused severe damages to the aircraft structure. These modifications suggested by Douglas included a completely new door locking system for the infamous cargo door. Several facts are still unknown, but neither Douglas nor the operators of the DC-10 took this service bulletin too serious. At this time, 49 aircraft were already manufactured and operated by following airlines:

1: DC-10 prototype, later for American 2: Mc Donnell-Douglas test flights 3: American Airlines 4: United Airlines 5: American Airlines 6: United Airlines 7: American Airlines 8: United Airlines 9: American Airlines 10: United Airlines 11: United Airlines 12: American Airlines 13: American Airlines 14: National Airlines 15: United Airlines 16: National Airlines 17: United Airlines 18: National Airlines 19: National Airlines 20: American Airlines 21: American Airlines 22: American Airlines 23: American Airlines 24: American Airlines 25: United Airlines		26: United Airlines 27: United Airlines 28: DC-10-40 prototype, later for Northwest 29: Mitsui / THY 30: American Airlines 31: American Airlines 32: United Airlines 33: Mitsui / THY 34: Continental Airlines 35: United Airlines 36: 2nd DC-10-40, later for Northwest 37: American Airlines 38: National Airlines 39: United Airlines 40: Continental Airlines 41: Continental Airlines 42: United Airlines 43: Continental Airlines 44: Continental Airlines 45: United Airlines 46: DC-10-30 prototype, later for KLM 47: Mitsui / Laker 48: American Airlines 49: American Airlines

Number 47, 48 and 49 were not taken up at this point of time, while number 1,2,28,36 and 46 were used by Mc Donnell - Douglas for different kinds of flight tests. Number 29 and 33 were still at Long Beach, but would be delivered to THY via Mitsui later that year. One month after the bulletin was issued, United Airlines completed the first modification. Here the modification chronology:

Date		Airline		Aircraft		Remarks
01/08/1972 12/08/1972 14/08/1972 18/09/1972 02/10/1972 06/10/1972 09/10/1972 11/10/1972 15/10/1972 16/10/1972 17/10/1972 20/10/1972 24/10/1972 30/10/1972 02/11/1972 09/11/1972 09/11/1972 14/11/1972 02/12/1972 06/12/1972 11/01/1973 23/01/1973 02/02/1973 17/02/1973 05/03/1973 15/03/1973 18/03/1973 28/03/1973 12/04/1973 02/05/1973 07/05/1973 11/05/1973 14/05/1973 23/05/1973 24/05/1973 29/05/1973 02/06/1973 18/06/1973		United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines United Airlines National Airlines United Airlines National Airlines American Airlines National Airlines National Airlines American Airlines American Airlines Continental Airlines American Airlines American Airlines American Airlines American Airlines Continental Airlines American Airlines American Airlines Continental Airlines American Airlines Continental Airlines American Airlines American Airlines Continental Airlines American Airlines American Airlines		46611/ 35 46614/ 45 46613/ 42 46605/ 15 46604/ 11 46610/ 32 46606/ 17 46602/ 8 46603/ 10 46609/ 27 46601/ 6 46612/ 39 46600/ 4 46607/ 25 46702/ 18 46608/ 26 46703/ 19 46504/ 7 46706/ 38 46701/ 16 46506/ 12 46509/ 21 46900/ 34 46505/ 9 46510/ 22 46503/ 5 46511/ 23 46902/ 41 46508/ 20 46514/ 31 46901/ 40 46502/ 3 46903/ 43 46512/ 24 46515/ 37 46904/ 44 46507/ 13 46513/ 30		Last UA modification (129 days)                   Involved in Windsor incident                   Last CO modification (330 days)   Last AA modification (350 days)

These are just the modifications made until Turkish Airlines aircraft #29 had the heavy fatal accident. Three days later, National Airlines suddenly discovered that their first aircraft, #14, has not been modified. The other THY aircraft, #33 didn't recieve the modifications either. Both THY aircraft were still at Long Beach at the time the service bulletin was issued!
Douglas inoficially planned three months for the modifications, but on October 3rd 1972 only 5 modifications have been made - and all by United Airlines. This was also the time when the FAA testified that service bulletin 52-37 was the solution for the DC-10 problems. United was also the first airline to modificate the whole fleet - 129 days after the bulletin was issued. At this point of time, neither THY nor American Airlines nor Continental Airlines have modified a single aircraft. American Airlines, the airline which was most involved in the DC-10 design and development, needed an average of 270 days (9 months!) to modify its fleet. It should also be noted that #5 (N103AA), the aircraft involved in the Windsor incident, was just modified after 255 days.
None of the aircraft initially ordered by the japanese leasing consortium Mitsui (inclusing also the non-delivered #47 for Laker) were on any list for modification. Mc Donnell - Douglas and THY blamed each other for the accident near Paris. A piece of paper which was not taken serious by anyone of the involved companies became very important overnight.