The 58-year-old who has not yet been named is reported to have fallen ill after taking her seat for the Edinburgh-bound flight on Wednesday.
Emergency services including police and paramedics rushed to the scene but she died on the aircraft at around midday.
"This flight from Palma to Edinburgh was delayed ahead of take-off after a customer became ill prior to departure,” a Ryanair spokesperson said in a statement.
"Paramedics boarded the aircraft after medical assistance was requested but the customer sadly passed away.
"Ryanair extends its deepest sympathies to the bereaved and is providing any assistance required."
The flight itself eventually took off three hours late after customers, who had been asked to disembark while the woman was treated, were boarded back onto the plane.
The Foreign Office said:"Our consular staff are supporting the family of a British woman following her death in Spain."
Local media reports say a post-mortem will now be carried out on Thursday.
In 2015, mother-of-two Davina Taverner, from Bolton, collapsed three hours into a Ryanair flight to Lanzarote after suffering heart problems in the toilets.
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