Flights between Newark, New Jersey and New Delhi are canceled until at least Monday, after evaluations found the air quality to be 75 times the World Health Organization's safety levels.
A representative of the airline told CNN they are monitoring advisories as the region is under a public health emergency.
The United airlines operates Boeing 777 a 267-seated aircraft on the route from Newark to Delhi comprising of 14 hours of journey.
The airline is also transferring affected passengers to other airlines.
The "foreign travel advice" section of the United Kingdom government's website, gov.uk, says, "Severe air pollution is a major hazard to public health in Delhi, and a serious concern in many Indian cities".
United Airline, while issuing a travel waiver for its customers with tickets to Delhi from November 9 through November 13, said customers could re-book these tickets on or before November 18 at no additional cost.
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It is not known if competing airlines like Virgin Atlantic, Etihad and KLM offered any similar waiver.
It is being feared that the smog in Delhi will hit tourism and foreign tourists will skip Delhi in favour of other cleaner destinations, said industry chamber Assocham.
Karan Anand, head-relationships, Cox & Kings, "We are not seeing any cancellations from tourists at this point. Even domestic tourists are avoiding Delhi".
New Delhi's Indira Gandhi Airport is by far the busiest in India handling more than 30 million passengers annually compared to Mumbai's 23 million and Bangalore's 12 million in second and third place. Air pollutants, especially PM 2.5 and PM10 levels have been over ten times higher than permissible.
Besides hampering visibility on road, the situation has become a public health emergency, and prompted schools to shut down in its wake.