The UK's Transport and General Workers' Union has called for an investigation into "suspected toxic gas poisoning of an airline cabin crew", according to a news source.
Two Flybe crew members reportedly collapsed and became violently ill on a flight between Birmingham and George Best Belfast City Airport.
Flybe said all of its aircraft were manufactured and maintained to the highest industry standard.
In a statement, Flybe said: "Any incidents involving sickness experienced by cabin crew, flight crew or passengers are taken very seriously by the company, with appropriate medical support always provided."