Dozens of Britons are being flown back to the UK from Libya following unrest, as the government faces criticism over its response to the situation.
A plane chartered by oil companies for employees, with 78 passengers, has arrived at Gatwick. A government-chartered flight has also left Libya.
Stranded Britons have criticised the government's response to the crisis.
Foreign Secretary William Hague said delays in supplying planes to evacuate Britons had been "infuriating".
The government-chartered flight is now on its way back to the UK with a stop-over in Malta.
It follows the arrival at Gatwick of the flight chartered by oil companies, which the airport said carried 78 passengers. Earlier reports suggested more people had been on board.
An RAF Hercules C130 aircraft has arrived in Tripoli to collect British nationals.
A second military plane is on standby in Malta if needed.
The Foreign Office said "a number of additional planes" could be sent to Libya throughout the day.
Mr Hague told BBC Radio 4's Today programme there should now be "more than enough capacity" for the remaining Britons in Tripoli to be evacuated.
"That should have been the case yesterday morning and I am very sorry to those people who could not get out yesterday," he said.
The foreign secretary said three planes were supposed to have landed in Tripoli on Wednesday.
"Three planes were meant to go in yesterday morning and, for a variety of reasons which I found infuriating but nevertheless we have to deal with, none of those three planes were able or willing to take off," added Mr Hague
He said Britons who had been waiting at Tripoli airport on Wednesday had now been left Libya.
In a statement issued on Wednesday night Mr Hague announced a review of the government's evacuation response, looking at "long-standing arrangements for aircraft evacuations" to establish whether delays had been "a coincidental series of unavoidable setbacks, or a systemic flaw".
The foreign secretary will later chair a meeting of Cobra, the government's emergency planning committee.
Helena Sheehan, 66, one of the passengers who landed at Gatwick earlier, said she had just experienced "some of the worst hours of her life".
"Libya is descending into hell," she said.
"The airport is like nothing I've ever seen in my whole life. It's absolute chaos. There's just thousands and thousands of people trying to get out."
The British Red Cross has deployed a team of volunteers to Gatwick airport to provide support to Britons being evacuated.
Mr Hague's statement came after some stranded Britons had accused the government of doing nothing to help them while other countries flew their citizens home.
Shadow foreign secretary Douglas Alexander has said the government was "slow off the mark" and said ministers should convene the emergency committee Cobra to co-ordinate the evacuation plans.
BBC security correspondent Frank Gardner said an SAS contingent has been put on standby for emergency deployment to parts of Libya, backed up by paratroopers of the Special Forces Support Group.
Our correspondent said: "With the situation for some British nationals in Libya fast deteriorating, it's part of a range of options being considered by the government to rescue those stranded in the North African country.
"Exact numbers and the locations of any staging areas are being kept secret but it's a scenario that British Special Forces have trained hard for - landing in the midst of a dangerous and chaotic situation then securing the safe passage out of stranded Britons, all hopefully without a shot being fired."
As well as a series of flights, the Royal Navy frigate HMS Cumberland is also due to arrive off the Libyan coast to help with the evacuation if needed.
Earlier Mr Hague had said the government would send "as many planes as necessary" to bring Britons home.
The foreign secretary postponed a planned visit to Washington on Thursday in order to remain in London and lead the Foreign Office's response to the crisis.
Several other countries, including France, Russia and the Netherlands have already evacuated some of their citizens.
UK nationals wishing to register an interest in flights out of Libya should call the following numbers: 020 7008 0000 from the UK or 021 3403644/45.
The Foreign Office is advising against all but essential travel to Libya.
Around 3,500 Britons had been living in Libya before the crisis but most of those are thought to have left in recent days.
However, there is particular concern for some British oil workers thought to be stranded in isolated desert camps.
'Held to account'
They are struggling to make contact because the phone networks have been disrupted and their supplies of food and water from Libyan cities are running out.
"Some we know have been subjected to attacks and looting. They are in a perilous and frightening situation," said Mr Hague.
After a week of upheaval in Libya, protesters backed by defecting army units are thought to have almost the entire eastern half of Libya under their control.
The country's beleaguered leader Colonel Muammar Gaddafi, who has been in power for 42 years, has vowed to fight to his "last drop of blood" rather than leave the country.
Mr Hague told the BBC the "odds were stacking up" against Col Gaddafi, adding: "We have a government, or the remnant of a government, here which is prepared to use force and violence against its own people."
He said the Libyan leadership will be "held to account" for crimes against its people.