The R Line and G Line are still on schedule to open this year, RTD officials said during a news conference on Tuesday.
The G Line -- which will run between Union Station and Wheat Ridge -- was said to begin service in the fall.
On Tuesday, RTD announced the G Line can't open until the ongoing problems with the A Line are resolved.
They admitted the line has a software crossing fix that must be completed before it can begin service. Its official start date was not announced.
The A Line, famously known as the train to the plane, is on-time 87 percent of the time and boasts 18,000 riders on weekdays, according to RTD. Although the on-time percentage seems high, RTD General Manager Dave Genova says it's unacceptable.
"Now that's not good enough. We want to be at a minimum of 90 percent or better," Genova said.
The R Line, touted as a 22-mild stretch from Peoria to Lincoln, should open in winter 2016. It does not face the same issues the G Line does.
Also announced was free, electric vehicles coming to the 16th Street Mall.
Tuesday's meeting will serve as the first of quarterly updates the transit service will provide.
#RTD GM says it wants to be candid and transparent regarding rail line progress— Vicente Arenas (@vicentearenastv) October 18, 2016