A number of flights to UK airports have been forced to land or divert following reports of "smoke smells".
Precautionary landings were reported from flights travelling to and from Dublin, Manchester, Liverpool and Jersey.
Liverpool John Lennon Airport said the smells appeared to be connected with "atmospheric conditions".
British Airways, Easyjet and Aurigny confirmed reports of smells on flights were linked to weather conditions.
A spokesman for John Lennon Airport said there were three "precautionary landings" following reports of smells in the cockpit of the planes.
Merseyside Fire and Rescue Service said crews were called to the airport at about 07:39 BST and supported airport fire personnel, who boarded a passenger jet.
- Easyjet confirmed a service between Liverpool and Zakynthos had to return to Liverpool, a flight from Malaga to Liverpool made a precautionary landing at the airport, and a service from Manchester Airport flying to Hamburg also had to return
- Flybe said crews aboard a service from Cardiff to Dublin took "precautionary action" when they detected the smell of fumes, but the aircraft was able to land as normal. It also confirmed another service - travelling from Manchester to Paris - was returned due to a "fume-like smell", but landed safely
- An Aurigny service travelling from Guernsey to Bristol had to head back to the Channel Island due to the smell, but was returned to service after checks by engineers
- Emergency services were called to a British Airways aircraft landing in Jersey "as a precaution" due to the conditions
'Like a firework'
Steph Whitehead, from Liverpool, was on Easyjet flight EZY1841 which was due to travel from Manchester Airport to Hamburg at 12:25 BST.
She said the flight was airborne for about 20 minutes when the captain said there was "smoke in the cockpit", and returned the plane to Manchester.
Ms Whitehead said passengers in the cabin also caught a whiff of the smoke, which "smelled like a firework", adding people were "a bit worried at first" about it.
Passengers were escorted away from the plane by fire crews, before being put back on the same plane for departure.
NATS, a company that provides air traffic control services in the UK, said it had facilitated "a number" of diversions from aircraft reporting fumes being detected in the cockpit.
All of these flights had landed safely, a spokesman added.
It comes following reports of an "unusual" reddish sky across parts of England, which experts are attributing to the remnants of Hurricane Ophelia dragging in tropical air and dust from the Sahara, as well as debris from forest fires in Portugal and Spain.
The Met Office said: "The same southerly winds that have brought us the current warmth have also drawn dust from the Sahara and smoke from wildfires occurring over northern Iberia (Spain/Portugal) to our latitudes."