The proposed deal would have created a fifth major player among US carriers, challenging American Airlines, Delta, United and Southwest, which together have around 80% of the market.
However, a judge in Boston ruled the proposed merger would harm Spirit’s passengers, who benefit from its Ryanair-style business model. JetBlue, which this summer will operate transatlantic services to London, Edinburgh and Dublin, is regarded as a hybrid carrier.
Both companies said they disagreed with the ruling and were considering their next steps.
It is the second blow to JetBlue in a matter of days; last week its chief executive Robin Hayes was forced to step down on medical grounds.
