As its 500 pilots remain on strike for higher wages and work rule changes, U. S. airline Spirit said it was extending its flight cancellations through Thursday.

The South Florida Sun-Sentinel reported on Tuesday that the airline that normally flies 150 flights a day has been grounded since June 11.

It would add an additional flight between Fort Lauderdale, Fla., and San Juan, Puerto Rico, on Wednesday, but it would not honor Spirit tickets, JetBlue Airways has said.

According to official reports, as pilots maintained their picket lines, negotiations continue with pilots at an undisclosed location in Fort Lauderdale.

"Our demands are still the same," Head of the pilots' union Capt. Sean Creed said on Monday.

The airline offered pilots a 30 percent raise over a five-year period, then issued a statement that said the increase was 47 percent when seniority pay was included in the calculation.

"I am concerned that our employees are being used in a broader political game that may not be in the interest of their careers or their families," Spirit Chief Executive Officer and President Ben Baldanza said in a statement.

Assertion was called an exaggeration by Creed. He said that the demands were not part of an industry-wide movement to raise salaries. (With Inputs from Agencies)