(Reuters) - No-frills air travel pioneer Spirit Airlines filed for bankruptcy protection on Monday, after struggling with a long run of quarterly losses, failed merger attempt and upcoming debt maturities.

Spirit, known for its bright yellow livery, is the first major U.S. airline to file for Chapter 11 since 2011.

It has not posted a full-year profit since 2019 and has been facing an uncertain future after the collapse of its $3.8 billion planned merger with JetBlue Airways in January.

Below is a list of events, starting with a long-drawn bidding war for the airline two years ago:

Feb. 7, 2022 Spirit Airlines, along with budget carrier

peer Frontier Group Holdings, unveiled plans

to create the fifth-largest U.S. airline in a

$2.9 billion tie-up to tighten competition

against traditional carriers.

April 5, 2022 JetBlue Airways made an unsolicited $3.6

billion bid for Spirit, snarling its merger

plans with Frontier and starting a U.S.

low-cost carrier battle.

May 2, 2022 Spirit board rejected JetBlue's offer, saying

it had a low likelihood of winning approval

from government regulators on antitrust risks.

May 16, 2022 JetBlue launched a hostile all-cash takeover

bid for Spirit Airlines, two weeks after the

rejection of its earlier offer.

May 19, 2022 Spirit urged shareholders to reject a hostile

bid by JetBlue, saying it was "a cynical

attempt to disrupt" its merger with Frontier .

May 23, 2022 Spirit CEO Ted Christie said it is unlikely

shareholders would vote against its proposed

merger with Frontier, to remain a stand-alone

entity if shareholders reject.

June 2, 2022 Frontier agreed to offer a break-up fee of

$250 million in a bid to secure its $2.9

billion bid for Spirit.

June 28, 2022 Spirit again rebuffs JetBlue citing antitrust

concerns, weeks after it raised offer with

higher break-up fee and new ticking fee,

amounting to a $3.8 billion bid.

July 27, 2022 Spirit Airlines canceled its sale to Frontier

Group Holdings after Spirit shareholders

balked at supporting it, weeks after Frontier

declined to further raise its bid, drawing

curtains on the bidding war with JetBlue.

JetBlue prevailed in the months'

July 28, 2022 long bidding war for Spirit Airlines after the

ultra-low-cost carrier

accepted its $3.8 billion buyout

deal.

Oct. 19, 2022 Spirit shareholders voted in favor of JetBlue

Airways' $3.8 billion takeover offer.

Dec, 9, 2022 Spirit offered as much as a 43% cumulative

weighted average pay raise to its pilots over

two years.

Jan. 10, 2022 Pilots at Spirit voted to ratify the contract,

which represents an economic gain of $463