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Flights began to resume late on Friday

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British Airways warns of 'huge impact' in coming days

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Unclear who responsible for cost of disruption

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Police say incident not being treated as suspicious

(Recasts headline, paragraph 1 with return to operations, adds

spokesperson's statement in paragraphs 4-5)

LONDON, March 22 (Reuters) - London's Heathrow Airport

resumed full operations on Saturday, a day after a fire knocked

out its power supply and shut Europe's busiest airport, causing

global travel chaos.

The travel industry was scrambling to reroute passengers and

fix battered airline schedules after the huge fire at an

electrical substation serving the airport.

Some flights had resumed on Friday evening, but the

shuttering of the world's fifth-busiest airport for most of the

day left tens of thousands searching for scarce hotel rooms and

replacement seats while airlines tried to return jets and crew

to bases.

Teams were working across the airport to support passengers

affected by the outage, a Heathrow spokesperson said in an

emailed statement.

"We have hundreds of additional colleagues on hand in our

terminals and we have added flights to today's schedule to

facilitate an extra 10,000 passengers travelling through the

airport," the spokesperson said.

The travel industry, facing the prospect of a financial hit

costing tens of millions of pounds and a likely fight over who

should pay, questioned how such crucial infrastructure could

fail without backup.

"It is a clear planning failure by the airport," said Willie

Walsh, head of global airlines body IATA, who, as former head of

British Airways, has for years been a fierce critic of the

crowded hub.

The airport had been due to handle 1,351 flights on Friday,

flying up to 291,000 passengers, but planes were diverted to

other airports in Britain and across Europe, while many

long-haul flights returned to their point of departure.

Heathrow Chief Executive Thomas Woldbye said he expected the

airport to be back "in full operation" on Saturday.

Asked who would pay for the disruption, he said there were

"procedures in place", adding "we don't have liabilities in

place for incidents like this".

Restrictions on overnight flights were temporarily lifted by

Britain's Department of Transport to ease congestion, but

British Airways chief executive Sean Doyle said the closure was

set to have a "huge impact on all of our customers flying with

us over the coming days."

Virgin Atlantic said it expected to operate "a near full

schedule" with limited cancellations on Saturday but that the

situation remained dynamic and all flights would be kept under

continuous review.

Airlines including JetBlue ( JBLU ), American Airlines ( AAL ), Air Canada ( ACDVF ),

Air India, Delta Air Lines ( DAL ), Qantas, United Airlines, British

Airways and Virgin were diverted or returned to their origin

airports in the wake of the closure, according to data from

flight analytics firm Cirium.

Shares in many airlines fell on Friday.

Aviation experts said the last time European airports

experienced disruption on such a large scale was the 2010

Icelandic volcanic ash cloud that grounded some 100,000 flights.

They warned that some passengers forced to land in Europe

may have to stay in transit lounges if they lack the paperwork

to leave the airport.

Prices at hotels around Heathrow jumped, with booking sites

offering rooms for 500 pounds ($645), roughly five times the

normal price levels.

Police said after an initial assessment, they were not

treating the incident at the power substation as suspicious,

although enquiries remained ongoing. London Fire Brigade said

its investigations would focus on the electrical distribution

equipment.

Heathrow and London's other major airports have been hit by

other outages in recent years, most recently by an automated

gate failure and an air traffic system meltdown, both in 2023.