Does National Guard Tuition Assistance (RIRP) cover online classes?

They will cover the school in your state. I took online classes from a community college nearby. I couldn't make it to regular classes. I did go in person to register and give them my forms from my state. Then I took the classes online. I would look at your states National Guard website and look for a contact at their Education Center for help with this.

Here are the basic criteria on their website:
Be in good standing with the State Military Forces (attend or make-up all drills and annual training)
Be accepted and enrolled in an undergraduate degree-granting program for a minimum of six (6) credit hours per semester or four (4) credit hours per quarter
Be a resident of the State of New York for a period of 186 days prior to using the program, excluding Active Duty periods

Each state is different, best bet is to contact your state education office. In my state you have to use federal tuition assistance for online schools that are based out of state, any online school that is headquartered in our state we can use state tuition assistance.