Further British chartered flights taking military rations to Hurricane Katrina victims are scheduled to leave RAF Brize Norton in Oxfordshire.
Aid flights from the UK are due to continue throughout the week
On Sunday the US asked the European Union and Nato to send emergency aid.
Two planes carrying the first batch of 500,000 standard issue ration packs - each containing enough food to last one person up to 48 hours - left on Monday.
Three more will leave for Little Rock, Arkansas, on Tuesday, to be followed by daily flights over the coming week.
The rations will be flown on from Arkansas to Texas, Mississippi and Alabama, where refugees evacuated from the hurricane disaster zone are currently based.
It is the biggest aid operation launched from the UK since the response to the Indian Ocean tsunami on 26 December last year.
Each 4lb (1.8kg) ration pack contained an average of 4,061 calories, the MoD said.
They comprise a variety of ready meals and snacks such as chicken stew with herb dumplings, lamb curry, French onion soup, rice pudding, biscuits, chocolate, chewing gum, coffee and tea.
A mini-stove and matches to heat up the food is included. Vegetarian versions are also being sent.
Each pack contains a mini-stove to heat up the food
Brig Chris Steirn, Ministry of Defence director of logistics operations, said: "When the request came in, we as a nation put our hands up immediately.
"These combat rations have a high calorific value, are easy to handle and are hugely useful in humanitarian operations."
He added: "The US have got a lot of troops deployed at the moment, consuming rations, and given the scale of this disaster, with 100,000 to 200,000 people displaced, these will keep them going for a few days."
The MoD could supply more of the four million ration packs it still had in store, he said.
Future aid deliveries could also include blankets, tents and cooking equipment.
"It is certain that as more refined US requests come in we will respond to them," Brig Steirn said.
Wing Cdr Mark Baker, RAF Brize Norton operations manager, said: "Our staff are working around the clock to get this done. It is an extra burden on us but it is one we take on willingly."
Military planes were not being used because they were engaged in Iraq and Afghanistan, and because added security was not needed for flights to the US, he said.