Delta Air Lines said it was cutting fares on practically all coach seats on all of its flights by 20 percent in an effort to lure more business travelers.

The fares require at least three days' advance reservation, but they have no minimum stay requirements, no penalties for reservation changes, and they are refundable.The travel can begin on Saturday, March 16, and the promotion will last indefinitely, a Delta spokesman said.

Fare sales are generally matched very quickly in the highly competitive airline industry, but none of the other carriers immediately put out announcements responding to Delta's move.