2127 GMT (4:27 p.m. EST)
There is no estimate on the duration of this additional delayed. Boeing has until 5:31 p.m. EST (2232 GMT) to get the Delta 4-Heavy rocket off the pad today.
2125 GMT (4:25 p.m. EST)
The countdown will remain holding at T-minus 5 minutes due to an alarm. Engineers need to check the situation before clocks can resume ticking. Liftoff will be delayed pasted 4:31 p.m. EST.
2128 GMT (4:28 p.m. EST)
The problem involves a momentary loss of signal for Range Safety equipment. Officials want to understand that problem before proceeding with the launch today.