OPM issued this afternoon its call letter for 2018 FEHB benefit and rate proposals which are due at the end of May. Here's a link to that letter.
Last year, the call letter came out in February which now holds the World's record for second speediest call letter issuance. Interestingly, in 2009, the outgoing George W. Bush administration's OPM did not preempt the incoming Obama administration's OPM by issuing the call letter before January 20, 2009. The 2010 call letter came out rather late on April 20, 2009.