They have scheduled an 11 a.m. news conference at the airport to make an "air service" announcement.
Allegiant flights from TCRA to Orlando, Fla., could start in late May or early June, a TCRA memo said last month.
That same memo had cited possible one-way introductory fares of $39 to $49, but the fare structure will be announced today, said TCRA Marketing Director Melissa Thomas.
"The fares typically level out at $69 each way with some seats higher and others lower," the TCRA memo said. "These low fares significantly boost travel by those who would not typically choose to travel by air."
Allegiant sells tickets online at its Web site (www.allegiantair.com), through its reservation center and through travel agents.
Allegiant, founded in 1997 and based in Las Vegas, operates a fleet of 130- to 150-seat planes going to Las Vegas, Orlando and Clearwater-St. Petersburg, Fla., from midsized and smaller airports across the nation.
The airline currently has Orlando service at Roanoke, Chattanooga and Knoxville, according to TCRA.
"When Allegiant initiated service, all three markets saw an immediate increase in passenger numbers," the TCRA memo said.
TCRA commissioners approved a proposal last month to invest more than $250,000 in ground handling services equipment and hiring new staff to take care of baggage and run a ticket counter for Allegiant.
Airport officials said they hoped the investment would entice other similar carriers to locate at TCRA.
Airport officials also insisted Allegiant would not affect TCRA service to Orlando via Delta Connection. Delta's service to Orlando is more focused on the business traveler, said TCRA Executive Director Patrick Wilson.
For more about TCRA go to www.triflight.com.