* UK begins repatriation of 110,000 travelers
* About 300,000 future bookings canceled
* Monarch becomes biggest UK carrier to go into administration
* Ryanair, easyJet, Wizz Air shares rise (Recasts, adds rivals' shares, quotes)
LONDON, Oct 2 (Reuters) - Britain's Monarch Airlines collapsed on Monday, stranding more than 100,000 travelers abroad after it fell victim to intense competition for flights to holiday destinations in Spain and Portugal.
The failure of Monarch, the largest British airline to go bust, will affect nearly 900,000 passengers in total and prompted the country's biggest peacetime repatriation effort.
Its demise added to turbulence in the European airline industry after Air Berlin and Alitalia filed for insolvency this year. Ryanair has also been forced to cancel thousands of flights because of problems finding enough pilots to fly them.
Shares of Monarch's rivals, easyJet, Ryanair and Wizz Air rose on Monday on the prospect of reduced competition and the chance to acquire some of its assets.
Monarch, based at Luton Airport north of London and in business since 1968, canceled about 750,000 future bookings and apologized to customers and staff.
"I am so sorry that thousands now face a canceled holiday or trip, possible delays getting home and huge inconvenience as a result of our failure," Monarch Chief Executive Andrew Swaffield told employees in a message.
"I am truly sorry that it has ended like this."
Monarch's finances deteriorated in 2016, after security concerns deterred travel to Tunisia, Turkey and Egypt and brought increased capacity for routes to Iberia. The decline in the value of the pound has also compounded its problems.
The airline was bailed out by its owner Greybull Capital a year ago.
"Monarch has really been a victim of a price war in the Mediterranean," Transport Secretary Chris Grayling told Sky News.
Grayling added that he expected many of Monarch's more than 2,000 staff to get jobs elsewhere.
"Monarch's problem was it was it was neither one thing nor the other. It was not really... a package holiday airline, nor was it really a low cost airline. I think it got rather squeezed in the middle," he added.
The British government has asked the Civil Aviation Authority (CAA) to charter more than 30 aircraft to bring home about 110,000 Monarch customers currently overseas, the CAA said. http://bit.ly/2wsQ5rQ
RIVALS STAND TO GAIN
Monarch has seen market share slip in recent years with the rise of budget carriers. It was Britain's fifth largest airline, and according to Euromonitor International, held 1.7 percent of the UK airlines market in 2017, down from 2.6 percent in 2012.
The collapse of Monarch could benefit its rivals.
"While we wait to see what comes out of the administration process there is no doubt that the pace of restructuring across Europe will be beneficial to yields as surplus capacity is reduced," analysts at Goodbody said in a note to clients.
Monarch had previously said it was talking to potential partners after a report that parts of its short-haul network would be sold.
Analysts at broker Cantor Fitzgerald said that it was likely that easyJet would bid for some of Monarch's assets.
"Monarch appears to be a good potential fit and we think that EZJ needs a new source of growth," the analysts said in a note.
The collapse will be a headache for some of the world's largest leasing companies, which financed its current fleet of 36 mainly Airbus jets, and for Boeing Co, which has sold the airline 32 of its 737 MAX aircraft. None of the planes has yet been delivered.
Monarch had been a regular pawn in the global battle for market share between planemakers as it shifted its loyalties between Airbus and Boeing.
Boeing secured Monarch's agreement to revert back to its jets in 2014 following a fierce contest against Airbus and Bombardier.
"NOT A TEXT, NOT AN EMAIL"
Monarch's last flight landed in Manchester from Tel Aviv at 3:19 a.m (0219 GMT) according to flight tracking service Flightradar24.
The website also showed 25 aircraft had been lined up to start repatriating passengers by 0600 GMT on Monday, including 10 from Qatar Airways already based in Europe on behalf of British Airways. An easyJet airplane and several charter aircraft were also part of the operation.
Hungarian low-cost carrier Wizz Air said it was offering to fly stranded Monarch passengers home from Tel Aviv for 119 pounds ($159) each.
Accoutants KPMG were appointed as administrators for the airline, and said that 860,000 passengers would be affected in all. Monarch said its companies that entered into administration include Monarch Airlines, Monarch Holidays Ltd, First Aviation Ltd, Avro Ltd and Somewhere2stay Ltd.
"We are working with the joint administrators and the CAA to do everything we possibly can to help minimize disruption where we can, but are under no illusion as to the problems this will cause," Monarch's Swaffield said.
While customers are being taken back to Britain, some who were due to travel out from Luton Airport said that the communication from the airline had been poor.
"I've had nothing from Monarch at all. It's absolutely, completely disgusting. Not a message, not a text, not an email," said Mary Quist from Milton Keynes in central England.
She had been sitting at a cafe in the airport for 6 hours, having been due to fly to Portugal.
"We can't even get to duty free to get some medicinal alcohol," she added.
($1 = 0.7488 pounds) (Writing by Alistair Smout in London; Additional reporting by Polina Ivanova in Luton, Subrat Patnaik in Bengaluru, Victoria Bryan in Berlin and Tim Hepher in Paris; Editing by Guy Faulconbridge and Keith Weir)