BBC | A plume of volcanic ash from Ethiopia has swept across the Red Sea through Oman and Yemen and reached Delhi, the India Meteorological Department (IMD) has said.
The eruption of the Hayli Gubbi volcano in Ethiopia - which was dormant for several thousand years - began on Sunday morning, sending an ash column thousands of feet into the atmosphere.
Several flights have been cancelled, delayed or rerouted in India because of the ash, with the country's aviation regulator asking airlines to "strictly avoid" affected areas.
The level of ash contamination is unclear, experts said, but it is unlikely to affect Delhi's air quality, which was "very poor" as per official readings on Tuesday.
Volcanic ash is a cloud of tiny, abrasive particles released into the atmosphere during an eruption. It can damage aircraft engines, contaminate airfields and reduce visibility, making it hazardous to flight operations.
"The affected altitude is between 8.5km (5.2 miles) and 15km above the sea level," Mrutyunjay Mohapatra, director general of IMD, told the BBC.
"It will temporarily affect satellite functions and flight operations. But it is unlikely to affect weather conditions or air quality. It reached northern India last night and seems to be headed towards China," Mr Mohapatra said.
According Skymet Weather, a private agency, it is difficult to predict how long the ash will take to disperse, but IMD estimates that Delhi's skies should clear out by Tuesday evening.
Aircraft operations have been disrupted as a result of the ash, with Air India cancelling 11 flights, while carriers such as IndiGo, Akasa Air and KLM also reportedly affected.
In a statement on X, IndiGo said it was tracking the situation "in coordination with international aviation bodies".
Mumbai Airport has asked passengers to check the status of their flights before leaving for the airport.
India's Directorate General of Civil Aviation issued an advisory to flight operators asking pilots to immediately report any suspected ash encounter, including engine performance anomalies or cabin smoke or odour.
The advisory also directs carriers to inspect aircraft operating near affected zones, and "suspend or delay operations to impacted airports if conditions deteriorate".
There are three levels of volcanic ash contamination - low, medium and high, with guidance on how long a pilot can fly in those concentrations before causing significant damage.
The level of contamination in this instance is unclear.
"Measuring contamination caused by volcanic eruptions take a lot of preparation. Sensors have to be deployed in advance. This particular volcanic eruption did not provide any room for preparation. So the level of contamination is not known," GP Sharma, president (meteorology and climate change) at Skymet Weather said.
Professor Atalay Ayele of Addis Ababa University told the BBC that the eruption stood out because the volcano had been dormant for thousands of years.
He said it had been unusually noisy but had not triggered significant seismic activity. The Hayli Gubbi volcano lies close to the Erta Ale, an area known for its active volcanic spots.
Volcanic ash clouds are rare. But when Iceland's Eyjafjallajökull volcano erupted in 2010, it caused global travel chaos. UK and European airspace was shut or partially shut, leading to the worst air-travel disruption since World War Two