Answer : 4. "Delhi Airport"
Explanation :

After facing several technical problems during flight operations, Air India has opened a warehouse facility in Delhi to facilitate storage of over 1,000,000 engineering spares. According to airline officials, the centralized warehouse, spread over 54,000 sq. ft., located adjacent to Terminal 3 in the cargo complex of the Air Cargo Logistics Division of Delhi airport, will improve the quick turnaround of the airline's flights operating from Delhi. ,