If you fail to get a confirmed train berth on train, you can upgrade yourself for an air travel. Air India and IRCTC have made this arrangement which is expected to be in place within a two to three days. As per the understanding wait-listed train passengers will be provided with the option to fly by Air India. However, they will have to pay a little extra.
First class train passengers will not have to pay anything for the upgrade but AC 2-tier passengers will have to pay upto Rs 2,000 for the upgrade.
It will also depend on the flight route (there should be flight route on the train destination) and availability of seats on the airline.