This is the second planning meeting to discuss science investigations and topics for the upcoming Grand Challenge Initiative -- Mesosphere/Lower Thermosphere (GCI-MLT). GCI-MLT is a follow-on to the successful GCI-Cusp campaign which has been ongoing since Dec 2018. GCI-MLT will have an expanded scope, with more international participation, a more geographically diverse set of observations, and more diversity in platforms (ground-based, balloon, aircraft, rocket, satellite) to address critical problems in MLT physics. GCI-MLT is an "umbrella" designed to coordinate and provide synergies for projects that will be funded through regular funding agencies. GCI-MLT does not provide funding, but it does provide a way for us all to work together and maximize the impact of our research. We work towards forming GCI-MLT around several existing rocket and balloon missions, and then developing proposals for other investigations (ground-based, balloon, rocket, aircraft, satellite) that will fit around these "anchor" missions.