However, officials at Heathrow and Gatwick, the main airports serving the capital London, reported dozens more flight cancellations as security measures remained tight for a fifth day.
British Airways, Virgin Atlantic and other airlines criticized BAA for needing until around dawn to communicate and implement fully the relaxed measures at Heathrow and Gatwick.
The carriers earlier criticised BAA's instruction for airlines at Heathrow to cut flights to ease congestion.
Under new government guidelines, passengers could only take aboard one small bag or case that held books, magazines, a laptop, mobile phones and other electrical devices, but were still denied non-essential liquids and gels.
Previously passengers could take aboard only essential items like money, tickets, keys, medicine and eyeglasses in see-through plastic bags.
BAA said the five other British airports it operates - Stansted,
Southampton, Edinburgh, Glasgow and Aberdeen - had put the new measures into effect by noon (1100 GMT) on Monday.
At airports throughout Europe, the backlog created by Thursday's arrests, and the subsequent stringent baggage restrictions, eased somewhat.
Suspects held longer
Air France passengers on flights to the United States were facing much shorter delays compared with three-hour waits at a Paris airport during the weekend.
The new measures in Britain were announced after the government downgraded the alert level to "severe," the fourth highest of five levels, from an unprecedented "critical."
Britain's Home Secretary John Reid said that the threat of attack was no longer imminent as police "believe that the main suspects in the alleged plot were arrested last week."
British authorities have arrested 24 people suspected of plotting to smuggle volatile chemicals on to several passenger jets headed for the United States with intent to set off explosions in mid-flight.
One was released on Friday. The remaining 23 suspects, including one who had a court hearing, can now be detained until Wednesday, London's Metropolitan Police said.
Mr Reid nonetheless warned that an attack remained "highly likely" as police investigated other suspected plots.
Following the British decision, the US Department of Homeland Security announced it was downgrading the threat level for inbound flights from Britain to "code orange" from "code red," its highest security risk alert.
The US Transportation Security Administration (TSA) now allows airline travellers to take in their carry-on luggage limited amounts of baby milk, personal prescription medicine and personal insulin. Four ounces of non-prescription medicine will be allowed as well.
However, all passengers in the United States will now be required to remove their shoes for X-ray inspection alongside their carry-on bags at airport checkpoints.
Pakistan investigation
Meanwhile, the global investigation into the alleged plot is turning increasingly to Pakistan and the Al-Qaeda network, amid media suggestions that worse plans could be afoot.
Photographs of British Al-Qaeda suspect Rashid Rauf also appeared in newspapers after Pakistani authorities claimed he was a "key person" in the plot.
In Pakistan, two senior officials told AFP that Britain's intelligence services had asked their Pakistani counterparts to trail Rauf after he entered the country. He was arrested on August 4 in the eastern city of Bahawalpur.
One of the officials said that British police carried out Thursday's raids after Rauf told Pakistani interrogators of the plot to blow up airplanes, which was apparently not yet known to British or US authorities.