Tests for Boeing Co new 787 Dreamliner are going more slowly than expected, but the company says it is still on track to deliver its first planes by the end of the year.

A Boeing spokeswoman said the company does not have a firm date for when the Federal Aviation Administration's in-flight certification process would kick off.

We remain on track for delivery this year, the Boeing spokeswoman said. Flight test programs are dynamic.

Some experts have said Boeing's deadline is too ambitious and delays are inevitable. The Dreamliner finally took to the air on December 15, after two years of repeated delays.

(Reporting by Kyle Peterson; Editing by Gary Hill)