Question: Vitim Airport is a public use airport built in Vitim, Sakha (Yakutia) Republic, Russia during World War II for the Alaska-Siberian (ALSIB) air route used to ferry which policy aircraft, formally titled "An Act to Promote the Defense of the United States?

Context paragraphs:
Kirensk Airport: Kirensk Airport (Russian: Аэропорт Киренск ) (IATA: KCK, ICAO: UIKK) is an airport in Irkutsk Oblast, Russia located 3 km west of Kirensk.  It handles small transport aircraft.  This airfield was part of the Yakutsk-Kirensk-Krasnoyarsk leg of the World War II Lend-Lease program Alaska-Siberian (ALSIB) air route.

Vitim Airport: Vitim Airport is a public use airport built in Vitim, Sakha (Yakutia) Republic, Russia during World War II for the Alaska-Siberian (ALSIB) air route used to ferry American Lend-Lease aircraft to the Eastern Front.

Northwest Staging Route: The Northwest Staging Route was a series of airstrips, airport and radio ranging stations built in Alberta, British Columbia, the Yukon and Alaska during World War II.  It extended into the Soviet Union as the ALSIB (ALaska-SIBerian air road).

South Pacific air ferry route in World War II: The South Pacific air ferry route was initially established in the 1920s to ferry United States Army Air Service aircraft to the Philippines.  As the Japanese threat in the Far East increased in 1940, General Douglas MacArthur planned that in the event of war, the United States Army Air Corps would play a major role in defending the Philippines.  The reinforcement by the Air Corps of forces in the Philippines, and later Allied forces in Australia, became the basis for developing the South Pacific air ferry route used during World War II.

Olenyok Airport: Olenyok Airport (IATA: ONK, ICAO: UERO) is a public use airport in Olenyok, Sakha (Yakutia) Republic, Russia.

Zyryanka West Airport: Zyryanka West Airport is an airport in Russia, located 8 km west of Zyryanka, Verkhnekolymsky District in the Sakha Republic of Russia.  It was built during World War II for the Alaska-Siberian (ALSIB) air route used to ferry American Lend-Lease aircraft to the Eastern Front.

Lend-Lease: The Lend-Lease policy, formally titled "An Act to Promote the Defense of the United States", (Pub.L.  77–11 , , 55 Stat.  31 , enacted  11, 1941 ) was a program under which the United States supplied Free France, the United Kingdom, the Republic of China, and later the Soviet Union and other Allied nations with food, oil, and materiel between 1941 and August 1945.  This included warships and warplanes, along with other weaponry.  It was signed into law on March 11, 1941 and ended in September 1945.  In general the aid was free, although some hardware, such as ships, were returned after the war.  In return, the U.S. was given leases on army and naval bases in Allied territory during the war.  Canada operated a similar smaller program under a different name.

Krasnoyarsk Northeast: Krasnoyarsk Northeast was an air base in Russia located 4 km northeast of Krasnoyarsk.  The airfield was the western end of the ALSIB Alaska-Siberia air route for Lend-Lease aircraft during World War II including Bell P-39 Airacobras and North American B-25 Mitchells.  The former airfield has been converted into apartment complexes.  There was an Antonov An-2 maintenance facility, which is now gone.  It was a utilitarian airfield with An-2, An-24, and An-6 aircraft, probably now based at Krasnoyarsk Yemelyanovo Airport.

Bodaybo Airport: Bodaybo Airport (IATA: ODO, ICAO: UIKB) is a regional airport built in Bodaybo, Irkutsk Oblast, Russia during World War II for the Alaska-Siberian (ALSIB) air route used to ferry American Lend-Lease aircraft to the Eastern Front.

ALSIB: ALSIB (or the Northern Trace) was the Soviet Union portion of the Alaska-Siberian air road receiving Lend-Lease aircraft from the Northwest Staging Route.  Aircraft manufactured in the United States were flown over this route for World War II combat service on the Eastern Front.

Supporting paragraphs: Vitim Airport Lend-Lease
Answer: Lend-Lease