UPDATE 1-Ryanair boss sees UK quarantine dropped or quashed by end-June

* Ryanair says legal papers due to be filed on Mon, Tues

* Airlines hope for emergency hearing this week - O'Leary

* Inbound bookings into UK Ryanair's only notable weakness
(Adds details, quotes)

By Natalie Thomas

LONDON, June 8 (Reuters) - Ryanair believes
Britain's courts will either strike down a 14-day quarantine for
international travellers this week or the government will drop
the measure before the end of June, boss Michael O'Leary told
Reuters on Monday.

Britain introduced the 14-day quarantine on Monday in a bid
to limit the spread of the novel coronavirus despite the threat
of legal action from some of the largest airlines that fly in
and out of one of Europe's biggest airline markets.

O'Leary said action proposed by British Airways-owner IAG
and supported by low cost rivals easyJet and
Ryanair seeking injunctive relief has a "high likelihood of
success." Legal papers are due to be filed on Monday or Tuesday,
he added.

"I think in their heart of hearts the government would like
the courts to strike it down because it would get them off the
hook. I think either the courts will strike it down this week or
the government will quietly drop it before the end of June,"
O'Leary said in a Reuters TV interview.

O'Leary, who has become one of the most outspoken critics of
the measure, calling it "completely useless and defective" on
Monday, said it has not stopped British holidaymakers planning
holidays abroad with bookings "building very strongly."

He said he expects flights from the United Kingdom to be
heavily booked when Ryanair ramps its daily flight schedule back
up on July 1 but that the quarantine would cause "untold
devastation" to British tourism.

Inbound bookings into the UK in July are the only notable
weakness Ryanair sees as confidence returns.

"It seems to be the usual peak summer holidays, families
going abroad for some much needed sunshine and outbound bookings
are very strong from Ireland, the UK, Northern Europe going to
Mediterranean," O'Leary said, namechecking holiday destinations
in Spain, Portugal, Italy and Greece.
(Writing by Padraic Halpin in Dublin; editing by Guy
Faulconbridge)