Safdarjung Airport was built in 1930 and was the main airport for Delhi until 1962.
Due to increasing passenger traffic at Safdarjung, civilian operations were moved to Palam Airport (later renamed to IGIA) in 1962.
Palam Airport had been built during World War II as RAF Station Palam and after the British left, it served as an Air Force Station for the Indian Air Force.

Units
No.
31 Squadron RAF
No.
34 Squadron RAF
No.
62 Squadron RAF
No.
76 Squadron RAF
No.
194 Squadron RAF
No.
232 Squadron RAF
No.
353 Squadron RAF
No.
681 Squadron RAF
Air Headquarters India Communication Squadron RAF
Base Air Forces, Southeast Asia Communication Squadron RAF
Supreme Commander's Headquarters (Air) Communication Squadron RAF
Palam Airport had a peak capacity of around 1,300 passengers per hour.
In 1979-80, a total of 3 million domestic and international passengers flew into and out of Palam Airport.
Owing to an increase in air traffic in the 70s and the 80's, an additional terminal with nearly four times the area of the old Palam terminal was constructed.
With the inauguration of this new international terminal, Terminal 2, on 2 May 1986, the airport was renamed as Indira Gandhi International Airport (IGIA).

The old domestic airport (Palam) is known as Terminal 1 and was divided into separate buildings- 1A, 1B, and 1C. Blocks 1A and 1B used to handle international operations while domestic operations took place in 1C. Today, block 1A became a dedicated terminal for domestic Air India, which is now demolished.
Block 1B was used as a departures-only terminal by all other domestic airlines, which is also demolished.
Block 1C was turned into a domestic arrivals-only terminal, and the newly constructed domestic departure block 1D is now used by all domestic low-cost airlines (GoAir, IndiGo, SpiceJet).
There is also a separate Technical Area for VVIP passengers.

Significant growth in Indian aviation industry led to a major increase in passenger traffic.
The capacity of Terminal 1 was estimated to be 7.15 million passengers per annum (mppa).
Actual throughput for 2005/06 was an estimated 10.4 million passengers.
Including the closed down international terminal (Terminal 2), the airport had a total capacity of 12.5 million passengers per year, whereas the total passenger traffic in 2006/07 was 16.5 million passengers per year.
In 2008, total passenger count at the airport reached 23.97 million.
In order to ease the traffic congestion on the existing terminals, a much larger Terminal 3 was constructed and inaugurated on 3 July 2010.
The new terminal's construction took 37 months for completion and this terminal increased airport's total passenger capacity by 34 million.
Apart from the three budget domestic airlines handled by Terminals 1C-1D, all other airlines operate their flights from Terminal 3.
Safdarjung Airport was built in 1930 and was the main airport for Delhi until 1962. Due to increasing passenger traffic at Safdarjung, civilian operations were moved to Palam Airport (later renamed to IGIA) in 1962. Palam Airport had been built during World War II as RAF Station Palam and after the British left, it served as an Air Force Station for the Indian Air Force. 
Units
No. 31 Squadron RAF
No. 34 Squadron RAF
No. 62 Squadron RAF
No. 76 Squadron RAF
No. 194 Squadron RAF
No. 232 Squadron RAF
No. 353 Squadron RAF
No. 681 Squadron RAF
Air Headquarters India Communication Squadron RAF
Base Air Forces, Southeast Asia Communication Squadron RAF
Supreme Commander's Headquarters (Air) Communication Squadron RAF
Palam Airport had a peak capacity of around 1,300 passengers per hour. In 1979-80, a total of 3 million domestic and international passengers flew into and out of Palam Airport. Owing to an increase in air traffic in the 70s and the 80's, an additional terminal with nearly four times the area of the old Palam terminal was constructed. With the inauguration of this new international terminal, Terminal 2, on 2 May 1986, the airport was renamed as Indira Gandhi International Airport (IGIA).
The old domestic airport (Palam) is known as Terminal 1 and was divided into separate buildings- 1A, 1B, and 1C. Blocks 1A and 1B used to handle international operations while domestic operations took place in 1C. Today, block 1A became a dedicated terminal for domestic Air India, which is now demolished. Block 1B was used as a departures-only terminal by all other domestic airlines, which is also demolished. Block 1C was turned into a domestic arrivals-only terminal, and the newly constructed domestic departure block 1D is now used by all domestic low-cost airlines (GoAir, IndiGo, SpiceJet). There is also a separate Technical Area for VVIP passengers.
Significant growth in Indian aviation industry led to a major increase in passenger traffic. The capacity of Terminal 1 was estimated to be 7.15 million passengers per annum (mppa). Actual throughput for 2005/06 was an estimated 10.4 million passengers. Including the closed down international terminal (Terminal 2), the airport had a total capacity of 12.5 million passengers per year, whereas the total passenger traffic in 2006/07 was 16.5 million passengers per year. In 2008, total passenger count at the airport reached 23.97 million. In order to ease the traffic congestion on the existing terminals, a much larger Terminal 3 was constructed and inaugurated on 3 July 2010. The new terminal's construction took 37 months for completion and this terminal increased airport's total passenger capacity by 34 million. Apart from the three budget domestic airlines handled by Terminals 1C-1D, all other airlines operate their flights from Terminal 3.
Indira Gandhi International Airport