Holidaymakers expecting to fly home via Houston in Texas could face delays of up to a week as the impact of tropical storm Harvey is felt more widely across the US.

George Bush and Hobby airports in Houston were closed and flights from the UK cancelled as a result of the category 4 hurricane, which hit the state last Friday (August 28).

More than 20 people are reported dead due to record rainfalls which have left large parts of the Texas city under water.

A night-time curfew has been imposed indefinitely to head off looting in the fourth most populous city in the US.

Thousands of residents have fled their homes in search of emergency shelter amid severe flooding and more than 13,000 have been rescued from affected areas.

USAirtours has 60 passengers due to travel on fly-drives around New Orleans – nearly 350 miles from Houston – in the next two weeks and 150 passengers due to fly home via Houston from all over the US, including Florida, Mexico and the Caribbean, in the next few days.

United Airlines said the first chance to re-route customers out of other US airports would be September 4. USAirtours is rebooking accommodation – clients will have to pay locally but the operator has pledged to reimburse them.

The Foreign Office travel advice is to track weather updates and follow local authority advice.

Scattered thunderstorms could trigger flight delays at Chicago, Dallas-Fort Worth, Denver, Detroit, the New York area, Orlando, Philadelphia, Phoenix and Washington DC.

British Airways is allowing passengers booked to travel up to and including September 7 to or from Houston, Austin or New Orleans to delay travel until September 20.

Other flights this week are being kept under review, pending the latest information from the airport authorities and the emergency services dealing with the flooding, the airline said.

“The safety of our customers is always our top priority and we are in regular contact with the airport authorities as the storm moves through the area,” BA added.

“Given the uncertainty caused by the bad weather, if you are due to travel to or from Houston, Austin or New Orleans with British Airways up to and including Thursday, 7 September, even if your flight is still shown as operating, you can delay your travel up to and including Wednesday, 20 September.”

Virgin Atlantic passengers travelling to, from 
or through Austin, Houston or San Antonio can rebook free of charge until September 20.  The port of Galveston, Texas, 
has shut, affecting cruise lines.

Houston Airport System spokesman Bill Begley told the Houston Chronicle that officials are assessing the situation on a daily basis.

He said the airports will open when the weather clears, personnel can get to the sites to support flights, and roads are no longer flooded so passengers can safely get to and from the airport.

“We’re not going to put a deadline on this,” he said on Monday. “It’s going to be when it’s safe for everyone.”

More than 54 million passengers used the Houston Airport System last year.

Carnival Cruise Line diverted three of its ships to New Orleans, while the August 31 sailing of Carnival Valor has been cancelled.

Royal Caribbean diverted Liberty of the Seas to Miami and cancelled its sailing last Sunday.

In a statement released on Wednesday Carnival Cruise Line said: “Due to extreme flooding conditions in Texas caused by Hurricane Harvey, officials in Galveston are unable to predict with any certainty when the Port of Galveston will re-open, but now expect it will remain closed until late this week.

“As a result, Carnival’s three Galveston-based ships, Carnival Freedom, Carnival Valor and Carnival Breeze, will all stop in New Orleans over the next two days to allow guests to disembark if they wish to make independent arrangements to return home or travel to another location.

“Alternatively, if their schedule allows, guests can elect to stay on board the ships, which will depart New Orleans between Tuesday and Wednesday. All three ships will head towards Galveston to be in position to enter the port as soon as it re-opens.

“Based on the uncertainty of when specifically the ships will be able to dock in Galveston, the Aug. 26 sailing of Carnival Freedom, the Aug. 27 voyage of Carnival Breeze, and the Aug. 26 and Aug. 31 sailings of Carnival Valor are now cancelled. A full refund will be provided to all guests who were scheduled on these cruises.

“Additionally, a 25 percent future cruise credit will be applied to their next reservation with Carnival if booked within the next 60 days.

“The safety and wellbeing of our guests and team members is our foremost priority. Our thoughts and prayers are with everyone impacted by Hurricane Harvey.”