300px|thumb|right|Lokalizacja Medan na planie Indonezji
'''Katastrofa lotu Mandala Airlines nr 091''' - katastrofa, do której doszło Sumatrze (tragedii rejsu nr 152, Garuda Airlines, który 26 września 1997 roku rozbił się także w okolicach Medan (234 zabitych) - największa katastrofa lotnicza w historii indonezyjskiego lotnictwa. 

==Przebieg tragedii i relacje świadków==
Rankiem 5 września 2005 roku, rejs nr 91 wystartował z miasta Medan do stolicy Indonezji - Dżakarty. Międzynarodowy Port Lotniczy Polonia - który opuścił - znajduje się w samym centrum gęsto zaludnionego miasta. 
Załoga utraciła kontrolę nad maszyną już kilka chwil po starcie. Według naocznych świadków, Boeing 737-200 (nr. rejestracyjny: PK-RIM) wpadł w chaotyczny ruch, wskutek którego uległ zmianie jej tor lotu. 
O godzinie 9.40, odrzutowiec runął na gęsto zaludnione osiedle mieszkalne, co przyczyniło się do zwiększenia liczby ofiar. Na pokładzie feralnego samolotu znajdował się gubernator Północnej Sumatry - Rizal Nurdin, a także jego poprzednik - Raja Inal Siregar. Obaj znaleźli się wśród zabitych.     

Jeden z ocalałych pasażerów lotu nr 91 - Freddy Ismail - stwierdził: ''"Po starcie, samolot zaczął się naprawdę trząść i zaraz później, nagle, runął na główną ulicę."''

Upadek wywołał tragiczny w skutkach pożar.

==Liczba ofiar==
Spośród 112 podróżnych, śmierć poniosło 96 ludzi. Z pięcioosobowej załogi nie ocalał nikt. Życie straciło także 44 mieszkańców okolicy. Większość z ocalałych pasażerów zajmowała miejsca w tylnej partii samolotu. 

{{Infobox Airliner accident|name=Mandala Airlines flight 091|
Crash image=Medan in Indonesia.png|250px|Image caption=Location of Medan in Indonesia.(possible crash site)|
Date=September 5, 2005 |
Type=Failure to takeoff |
Site=Medan, Indonesia |
Fatalities=101 + 47 |
Aircraft Type=Boeing 737-200 |
Operator=Mandala Airlines |
Tail Number=PK-RIM |
Passengers=112 |
Crew=5 |
Survivors = 16 |
}}

On Boeing 737-200 jetliner operated by '''Medan, Indonesia. 

Dozens of houses and cars were destroyed, and at least 39 persons are reported to have perished on the ground. Later it was reported that at least 16 persons survived the accident, with 104 of those on board known to have died including 3 babies. Most of the survivors are thought to have been seated at the rear of the aircraft, though some have reportedly since died from their injuries. Most of the dead were Indonesian, although at least one Malaysian, Ti Teow Chuan from Sabah, was reported dead. Rizal Nurdin, the governor of North Sumatra at the time, and Raja Inal Siregar, the former governor, were among the dead.

The crash was the sixth major incident involving commercial airliners since August 1 2005. The others were, in chronological order: Air France Flight 358; an ATR-72 crash in the Mediterranean Sea; Helios Airways Flight 522 crash, killing 122 in Greece; West Caribbean Airways Flight 708's crash in Venezuela, killing 160; and TANS Peru Flight 204, killing 41 out of 100 people on board when it crashed in Peru. 

==Survivors==
Passenger Rohadi Sitepu told Metro Television from hospital that he and five other people seated in the back of the plane in Row 20 had all survived. "There was the sound of an explosion in the front and there was fire and then the aircraft fell," he said. Rohadi said he escaped the blazing wreck by jumping through the torn fuselage and fleeing on foot as four large explosions erupted behind him.  
  
Another survivor, Freddy Ismail, told El Shinta Radio from his hospital bed that the aircraft seemed to be experiencing mechanical difficulties after take-off. "After take-off, the noise of the engine suddenly became very loud and the aircraft began shaking intensely before it suddenly fell," he said.

==Aircraft and Airline==
The aircraft, registration PK-RIM, was built in 1981 and formerly belonged to Lufthansa where it was registered as D-ABHK "Bayreuth". The aircraft had passed extensive safety tests in June and should have been airworthy until at least 2013.

Mandala Airlines was established in 1969 and is one of several low-cost airlines that serve the vast Indonesian archipelago. It was 90-percent owned by a foundation set up by the Indonesian Army strategic reserve Kostrad (''Komando Strategis Angkatan Darat''). As of April 2005, Cardig International is the sole owner of Mandala Airlines. In October 2006, Indigo Partners announced it has acquired a 49% stake in Mandala Airlines with PT Cardig International Aviation retaining a 51% stake. It has 1,000 employees (at March 2007).[1]

==Causes==
The airline said it was too early to know the cause of the crash. Witness statements are contradictory, with some claiming that the plane rose to an altitude of 90 metres before appearing to shake (possibly indicating a stall) and veer to the left, while others say that the aircraft failed even to clear the landing lights (not ILS antenna as mentioned in many media) at the end of the runway before veering to the right and crashing immediately. 