Low atmospheric air pressure

On a recent flight, passengers on a flight from Newcastle to Sharm el Sheikh were informed that due to ‘low air pressure’ they would have to refuel in Crete en-route.
Why is this?
As a complete novice, I would have thought that with low atmospheric air pressure, the aeroplane would be under less force, thereby making it easier to ‘stay’ in the air, thereby making the flight more fuel efficient ???

Or is this to do with…with the increase in altitude, the density of air decreases. The reduced density means a lower number of air molecules entering the core engine. For the fuel/air mixture to maintain its stoichiometric ratio, the required number of fuel molecules must decrease to cater for the decreased number of air molecules.

Thanks for any replies.

I realize this post is 3 months old but since there are no replies, I thought I’d offer one.

Is it possible that the explanation was meant as “due to a low-pressure system”? As in, unforeseen weather, higher headwinds, bad weather ahead, requiring more fuel than planned?

Also, FWIW, jet/turbine engines do not have a stoichiometric ratio, that is only required for internal combustion engines running on gasoline/petrol.