The fare zones were retained and fares dropped slightly the following year.

Labor Day to the week before Thanksgiving is traditionally when fares drop 15 to 20 percent below summer rates.

The one-way fare between Washington and Miami will drop to $79, from $109.

After the change, the fare dropped to $460 and then fell again a few weeks later to $380.

From Jan. 15 to May 31 the fare drops to $1,029.

"But if you plan your trip in advance, and don't mind staying over the weekend, the fare drops to maybe $458."

On routes where United's new service will compete directly with Southwest, fares may drop further.

The average fare to the Caribbean on Continental, he said, has dropped 12 percent in the last four years.

On Eurotunnel, for example, one-way fares can drop to £39 each way.

On Sundays, the fares drop to 25 cents a person.