WASHINGTON (Reuters) - Two leading critics of President Barack Obama’s moves toward normal relations with Cuba introduced legislation on Wednesday seeking to temporarily halt commercial flights between the United States and the island because of security concerns. Republican Senator Marco Rubio and Democratic Senator Robert Menendez, both Cuban-American opponents of Obama’s Cuba policy, introduced the Cuban Airport Security Act. The measure would stop commercial flights until after a study of security measures and equipment at airports in Cuba. The U.S. government has granted several U.S. airlines permission to begin scheduled flights to Cuba, opening another chapter in the Obama administration’s efforts to improve ties and increase trade and travel with the former Cold War foe. A JetBlue Airways Corp passenger jet flew to Santa Clara, Cuba, from Fort Lauderdale, Florida, on Aug. 31. It was the first scheduled commercial passenger flight from the United States to Cuba in more than half a century. Commercial flights to the capital, Havana, are expected to begin later this year. Obama’s Cuba policy sharply divides the U.S. Congress.  Opponents, mostly Republicans but also a few Democrats, say he is moving too quickly to ease restrictions on travel and trade, given continuing human rights violations by its Communist government. Backers say it is time to try another tactic in dealing with Havana after more than half a century with no change under the previous policy. A version of the bill was introduced in the House of Representatives in July. There has been no announcement of when the measure might come up for a vote. 