The kick-off had to be delayed for 45 minutes courtesy a political rally in the capital.
But it was worth the wait as Air India produced a scintillating display of football to leave their opponents speechless.
Pradeep struck in third and 15th minute while Prakash Thorat scored the other in the 43rd minute. In the second half, the oil-men pulled two back within a span of two minutes through Kenistan (72nd) and Sachin Gawas (73rd).
But Air India sealed the match in the 88th minute when Lepcha tapped it in off a Vijith Shetty corner.
The start was startling as Air India took off perfectly. They surged into the lead with Pradeep converting a direct free-kick off his left-foot and 12 minutes later, he doubled the score with another left-footer from outside the box.
Down by two early goals, ONGC found it hard to recover. Much desperate to pull things back after the initial setback, they went all out in the attack. They sorely missed Eric Brown in the midfield as much as they missed Bijoy Gurung in defence.
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To make matters worse, Air India scored their third goal when Thorat brilliantly flicked a low Shouvik Chakraborty centre with his left-foot from inside the box.
Changing over, Air India adopted a defensive approach allowing ONGC to make inroads. Kenistan volleyed in Kailash Patil's centre and off the restart, Gawas blasted it in past Air India goalkeeper Jagroop Singh in the very next minute.
The two goals lifted the spirit of the local team and had not an advancing Jagroop thwarted Kenistan in the 85th minute, the result could have been different.
But Air India had the last laugh when Lepcha made no mistake to capitalise on a Shetty corner.