Last month's average was also about 3 percent less than in the same month last year, and down around 36 percent from March 2005, according to monorail data.

At the current average of $4.46 in fares collected per passenger, the monorail would need a daily average of 27,579 riders to generate the $123,000 in fares per day needed to balance the monorail's books, according to financial estimates made in October 2006 by Fitch Ratings, a New York-based credit rating firm. At that time, Fitch Ratings said the system needed to take in an average of $123,000 in fares each day.

The monorail's daily operating costs and debt service total around $167,000, part of which is covered by ad sales, marketing partnerships and other lesser revenue streams.

Despite the short ridership numbers, monorail officials continue to vow that the system is due for a ridership growth spurt later this year.

"We are expanding and enhancing our marketing and advertising partnerships to increase awareness of the system and ultimately ridership," Ingrid Reisman, a Las Vegas Monorail Co. spokeswoman, said in a prepared statement.

For the first quarter of 2007, the monorail averaged 18,596 riders, down about 4 percent from the same quarter in 2006. In January and February, traditionally the monorail's lowest ridership months, the system averaged fewer than 17,000 riders per day.

When the monorail first opened in 2004, project leaders expected as many as 50,000 daily riders, a target that is no longer seen as realistic.

In the first three months of this year, daily farebox revenues were down just over 4 percent from the same quarter in 2006, averaging $86,874 per day.

The privately financed $650 million line has never made a profit and has seen its credit rating fall to "junk" bond status. The monorail is believed to have lost more than $20 million last year, though losses are being covered by a sizable reserve fund.

In the fall, a Fitch official said "default is a real possibility" as soon as 2008 if the monorail cannot find a way to make more money.

Taxpayers are not obligated to bail out the monorail should it go bankrupt. Minus some sort of voluntary bailout offered by the public or private sectors, bondholders and an insurance company would eat the loss.

Officials hope a planned $500 million extension to McCarran International Airport will boost ridership. Given the monorail's poor credit rating, it's unclear how the monorail company will fund that extension, planned to open as soon as 2011.

Monorail officials are also betting on the success of marketing partnerships with Strip hotels and conventions that are expected to show results in the form of more riders and increased revenues sometime this year.

And the monorail earlier this month launched a new advertising program allowing businesses to enter into short-term contracts to wrap trains and stations in advertising in connection with Las Vegas Convention Center events.

General Motors, Sony and Boost Mobile are among the first advertisers to participate in the program, officials said.

Originally, such ad programs involved multi-year contracts. Officials did not say how much revenue the new ad program is expected to produce.