Question: When was Umar Farouk Abdulmutallab attempting to detonate plastic explosives on Northwest Airlines Flight 253?

Context paragraphs:
Umaru Mutallab: Alhaji Umaru Abdul Mutallab (born 15 December 1939) is a Nigerian business and banking leader, and former minister of Economic Development under the military government of Murtala Mohammed.  He played a major role in introducing Islamic banking into Nigeria.  Mutallab was described by "The New York Times" as "among Nigeria's richest and most prominent men," by "The Telegraph" as being "one of Nigeria's most prominent bankers", and by "The Guardian" as being "one of the country's most respected businessmen".  Mutallab's son, Umar Farouk Abdulmutallab, is a student who attempted to detonate plastic explosives aboard Northwest Airlines Flight 253 on 25 December 2009.

Aftermath of the Northwest Airlines Flight 253 attack: Aftermath of the Northwest Airlines Flight 253 attack

Umar Farouk Abdulmutallab: Umar Farouk Abdulmutallab (Arabic: عمر فاروق عبد المطلب ; also known as Umar Abdul Mutallab and Omar Farooq al-Nigeri; born December 22, 1986) popularly referred to as the "Underwear Bomber", is a Nigerian man who, at the age of 23, confessed to and was convicted of attempting to detonate plastic explosives hidden in his underwear while on board Northwest Airlines Flight 253, en route from Amsterdam to Detroit, Michigan, on Christmas Day, 2009.

Northwest Airlines Flight 253: Northwest Airlines Flight 253 was an international passenger flight from Amsterdam Airport Schiphol in Haarlemmermeer, Netherlands, to Detroit Metropolitan Wayne County Airport in Romulus, Michigan, United States.  The flight was the target of a failed al-Qaeda bombing attempt on Christmas Day, December 25, 2009, in which a passenger tried to set off plastic explosives sewn to his underwear.  There were 290 people on board the aircraft—an Airbus A330-323E operated by Northwest Airlines, which had merged with Delta Air Lines the year before.  Had the attempt succeeded, it would have surpassed American Airlines Flight 191 as the deadliest aviation occurrence on U.S. soil and tied Iran Air Flight 655 as the eighth-deadliest of all time.  The incident was also the second in 2009 involving an Airbus A330, after the crash of Air France Flight 447 on June 1.  This was also the final accident/incident involving Northwest Airlines as it closed down a month later when it merged with Delta Air Lines.

Plastic explosive: Plastic explosive is a soft and hand-moldable solid form of explosive material.  Within the field of explosives engineering, plastic explosives are also known as putty explosives.

Northwest Airlines Flight 2: Northwest Airlines Flight 2 was a Lockheed Super Electra aircraft, registration NC17388, which crashed into the Bridger Mountains about 12 miles (19 km) northeast of Bozeman, Montana, on January 10, 1938.  All ten on board were killed in the accident, which was the first fatal crash of a Northwest Airlines aircraft or a Lockheed Super Electra.

Seaboard World Airlines Flight 253A: Seaboard World Airlines Flight 253A was a military charter flight carrying 214 American troops bound for South Vietnam.  On July 1, 1968, the plane was intercepted by Soviet jets after it unintentionally violated Soviet airspace.  It was forced to land on one of the Soviet-controlled Kuril Islands with all 238 Americans aboard being detained for two days.

Reactions to the Northwest Airlines Flight 253 attack: Reactions to the Northwest Airlines Flight 253 attack

Northwest Airlines Flight 421: Northwest Airlines Flight 421 was a domestic scheduled passenger flight from Chicago, Illinois to Minneapolis, Minnesota that crashed on 29 August 1948.  The Martin 2-0-2 aircraft, operated by Northwest Airlines, suffered structural failure in its left wing and crashed approximately 4.1 mi northwest of Winona, Minnesota, about 95 mi southeast of Minneapolis.  A Civil Aeronautics Board investigation determined that the crash was caused by fatigue cracks in the wings of the aircraft, and recommended lower speeds and frequent inspections of all Martin 2-0-2 aircraft.  All 33 passengers and four crewmembers on board were killed.  The crash was the first loss of a Martin 2-0-2, and remains the worst accident involving a Martin 2-0-2.

Convention on the Marking of Plastic Explosives: The Convention on the Marking of Plastic Explosives for the Purpose of Detection is a multilateral anti-terrorism treaty that aims to prohibit and prevent the manufacture or storage of unmarked plastic explosives.

Supporting paragraphs: Umar Farouk Abdulmutallab Northwest Airlines Flight 253
Answer: Christmas Day, December 25, 2009