The local challengers played with 10 players for 70 minutes after defender Bello Rasaq was sent off in the first-half but they showed tremendous resilience to thrash the airmen.
In his first I-league appearance after switching from defending champions Dempo, Martins struck in the 13th, 32nd and 57th minutes while K Asif (65th) and C K Vineeth (80th) completed the rout.
Mickey Fernandes provided the lone reply for Air India with his 23rd-minute goal.
After a forgettable Federation Cup campaign where they were eliminated in group stage, United SC had more heartbreak in store as Rasaq was shown a red card minutes after taking the lead.
But they regrouped to finish with a 2-1 lead at the break.
The home side built up on a positive start and found the lead early in the 13th minute when Martins nodded home a nice assist from Shylo Malswamtluanga.
United SC suffered a blow in the 20th minute seeing their dependable central defender Rasaq sent off with a direct red card.
Referee Pratap Singh, who is one of the three referees to receive a professional contract recently, penalised Rasaq for dangerous play when the player had a collision with Air India striker Henry Ezeh. MORE
