Extra checks have been conducted on aircraft fuel at Belfast City airport after one delivery failed testing requirements.
A Flybe flight was delayed by the incident, with passengers kept on board the aircraft while an alternative fuel load was secured.
The incident happened on Thursday, with the 1530 flight to Leeds Bradford impacted.
Lord Jonathan Caine, a political aide to Northern Ireland Secretary Karen Bradley, was one of the passengers affected.
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The Conservative peer, who had accompanied Mrs Bradley on her visit to the Balmoral agricultural show earlier in the day, described the delay as "completely unacceptable" and "beyond ridiculous".
A spokeswoman for Belfast City Airport said: "All aircraft fuel arriving at Belfast City Airport is subject to stringent testing at every stage throughout the supply chain."
Commenting on the Thursday incident, she said: "One fuel delivery to the site did not meet our requirements and some minor delays were incurred as a result.
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"Precautionary and additional checks were made to all other fuel in storage in accordance with normal procedures."
A Flybe spokeswoman said the incident was a matter for the airport, as it was responsible for fuelling all aircraft.
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