First a general word of caution:
There is an enormous amount of private and public sector investment in sustainable aviation. You are unlikely to find excellent, underfunded opportunities in a market-driven industry with billions in annual venture capital and R&D spending. Furthermore, focusing on emissions from just aviation is analogous to an interest in global health but only focusing on interventions to address micronutrient deficiencies. It may be worthwhile to investigate, and you may find some giving opportunities, but don't be surprised if the best emissions mitigation options in the aviation sector are much less cost-effective than those in other sectors.
That said, if you do find excellent philanthropic opportunities in the aviation sector, they could be listed among general mitigation-focused climate recommendations (e.g. Giving Green). It does make sense to have a sustainable aviation expert investigating giving opportunities for EA-aligned climate funding organizations. The EA climate orgs do not have the bandwidth or technical expertise to holistically investigate giving opportunities across all emissions-intensive industries.
Realistically, I think it will take a few years to get up to speed on the sustainable aviation industry and develop enough technical depth to make funding recommendations. Recommendations will likely be in the form of lobbying governments to fund specific subprograms at federal research agencies. If you have key industry experts in your group, this timeline can be compressed. If you don't have a full-time connection to R&D in the aviation industry, it's likely the industry will move faster than your capacity to follow along and you won't be able to come up with good funding opportunities. Also without industry expertise, you may get captured by an institution. Institutional capture happens quite a bit in philanthropy. It's where a funder relies too much on the expertise of a grantee and subsequently conflates the grantee's industry knowledge and perspective with a genuine belief that the particular grantee is doing the most important work in the space.
Where you'll find expertise:
- National Academies research reports on aviation (start here)
- ARPA-E technology managers on aviation
- NASA's Aeronautics Research Mission Directorate
- DOE labs like NREL or ANL
- Technology experts at sustainable aviation start-ups
- Aviation technology experts at VC firms
Lastly, on your criteria. You say you are open to all technologies and innovations, and short-listed an MIT lab working on new propulsion technologies. But you also list "target commercial date" as a key criteria in your selection process. Basic R&D and bench prototypes often take decades to go from lab to commercialization, if they ever make it there (most don't). A desire for immediate emissions reductions and a focus on R&D are conflicting considerations. If immediacy is your goal, it will likely be focused on displacing emissions from short-haul and regional flights with electric aircraft / eVTOLs, though I think you won't find any philanthropic opportunities here. If R&D is your goal, consider the much broader research areas that could influence aviation such as lightweight materials, batteries, renewable fuels, and even research on competing transportation modes.
If I had to pick interventions in the aviation space that are likely underfunded, I'd focus on atmospheric research to better predict and understand the impact of contrails on radiative forcing, and real-time aircraft re-routing / altitude adjustments to reduce contrail formation (see: Our World in Data post on aviation emissions, research on contrail formation). One could image an extension of air-traffic control that uses contrail formation risk to direct planes much as they do with real-time weather data for flight risks and to avoid turbulence.