President Donald Trump has increasingly turned to the military to help carry out his immigration agenda, including sending additional troops to the US-Mexico border, using military aircraft to deport migrants, and opening military bases to house them.

The official, speaking on the condition of anonymity, said the C-17 aircraft had departed for India with migrants aboard but would not arrive for at least 24 hours.

The Pentagon has also started providing flights to deport more than 5,000 immigrants held by US authorities in El Paso, Texas, and San Diego, California.

So far, military aircraft have flown migrants to Guatemala, Peru and Honduras.

The military flights are a costly way to transport migrants. Reuters reported that a military deportation flight to Guatemala last week likely cost at least $4,675 per migrant.