July 11 (Reuters) - Democratic Senator Richard

Blumenthal said a proposed partnership between United Airlines

and smaller JetBlue Airways ( JBLU ) could harm

competition and lead to fewer and more expensive options for

consumers.

In a letter seen by Reuters, Blumenthal asked United CEO

Scott Kirby and JetBlue ( JBLU ) CEO Joanna Geraghty to answer questions

about their "Blue Sky" tie-up to allows travelers to book

flights on both carriers' websites, while interchangeably

earning and using points in their frequent flyer programs.

Blumenthal asked the airlines to disclose records about the

partnership and future plans, adding he is concerned about any

deal "that may harm full and fair airline competition and lead

to fewer and more expensive options for travelers, particularly

in the New York City area."