Former Employer Sent Cease And Desist Claiming Ip Infringement Of Personal Project I Built On My Own Time

Location: Virginia

The Situation:

I was already a licensed pilot before being hired. During my employment, I built a personal project on my own time: a civilian VFR flight planning app for private pilots like myself.

The app is built entirely with open-source tools (React, TypeScript, Cesium, etc.—all publicly available, widely used technologies). All data in the app comes from publicly accessible sources: FAA databases, public airspace information, public weather sources etc, none of which they used.

About a month in, I posted about my project on LinkedIn. The company's CEO liked my post. I have screenshots. No one ever told me to stop or raised concerns.

I received "Exceeds Expectations" on both my 30-day and 90-day performance reviews. My manager noted my "personal interest in flying" as an asset.

6 months after the CEO liked my post, they fired me and sent a cease and desist claiming my personal project violates their IP Assignment Agreement I signed. They are demanding I stop all development or they will pursue legal action. I built this app in public for about 6 months, and only once I added a $5 paywall to my application did I get fired and get a cease and desist letter. I've since taken a paywall off my app, however my app is no longer public at this point until I get more understanding of my legal situation

My stronger points

• No proprietary technology: Everything I used is open-source. These are tools millions of developers use daily. They cited the overlapping tech stack in their cease and desist as evidence, but none of it is proprietary to them.
• No proprietary data: All data comes from public FAA sources and other publicly accessible databases. Nothing came from their systems.
• No copied code: They have not claimed I copied any of their code, because I didn't.
• Different markets: They make software exclusively for military/government clients. They have zero civilian products. My app is for individual private pilots.
• My expertise came from being a pilot, not from them.
• Personal time development: GitHub commits show ~75-80% of work was nights/weekends. Also no development was done on their systems, all on my personal computers.
• CEO's public engagement: Their CEO liked my LinkedIn post about the project, then 5 months later claimed it was unauthorized.
• IP Agreement defect: The agreement says inventions are assigned "except as provided in 'Exception to Assignments' below." That section doesn't exist in the document.

My Weak Points:

• First commit was 3 weeks after my start date
• Both products are "flight planning software" in the broadest sense
• ~20-25% of commits were during business hours (I worked remotely however, so some of my work was done during lunch breaks. I always worked my full workday no matter what.)
• No written evidence of wanting to build this before employment

The Agreements:

IP Assignment Agreement specifies Virginia law, binding arbitration in Fairfax County under AAA rules.

This app is not a business yet, and is just a personal project of mine that I eventually would like to try and make a business. I know nothing about how lawsuits work, and have never been sued before so I've only been building this app in private at this point. How likely is it that they have any rights over this? Their IP agreements are very vague as are most companies. I will likely reach out to a local attorney as well, but looking to just get some initial advice and perspective on my situation.

Thanks in advance.