The carrier told workers on Tuesday that it would stop publishing its customer relations phone number, which will be turned off altogether. Beginning in April, the workers will add customer-relations duties, which involve issues or complaints after travel.

United spokeswoman Robin Urbanski said the airline is able to respond better to customers who write, since they often include more detail, making it possible to provide a more specific response. "We clearly have the deep industry expertise to help our guests navigate through their options."

United also said that starting this month, it will begin urging customers to use e-mail or letters instead of calling its customer-relations phone number for complaints or compliments. The line will be shut off at the end of April.

Phone reservations agents in Chicago and Honolulu will be cross-trained to respond to written customer feedback too.