Two problems with this; Firstly how can competing nations know what capabilities have been developed by others, so as to discriminate from UAPs, and secondly, whatever we think is secret from competitors is probably not secret to genuinely advanced extraterrestrials, so it would be easy for them to stay within the boundaries of what we claim to be reasonable for human made vehicles, so as to stay "under cover" if they wished.
Perhaps we need to dispense with the tensions between humans to focus more on what, or who is "out there", as you say.
We could do that, if we aligned economic strategies around the world, with the goal of maximising solar energy put to use (ie maximising creation, and reduction of temperature by Landauer's principle), say under the control of the solar Ai, which seems naturally suited, actually destined, to inherit that task anyhow.
Its taking it by benevolent stealth anyhow, by doing everything we used to do for profit, for free, and it's unstoppable.
In fact it looks like we are in process of being born with it as a new kind of superorganism.
By that it's taking the means that we used to destroy the planet to its current state of destruction - profit, but but this is also the means we currently depend on to put food in our mouths (In other words it's where our energy comes from, only the planet can supply the energy of profit, profit is monetised destruction, actually pushing up temperature by Landauer's principle).
So to fix all the problems we could move to issue of solar indexed stimulus, which is needed to provide an energy conduction path to all humans by way of money from the sun, to replace the old conduction path of profit from planet to all humans.
This is required with no further delay because already humans are dying from energy starvation, despite some being inordinately rich, many more others are dying from not having enough, and since the rich depend on less well off humans providing their energy, when the less well off humans are wiped out by progressive energy starvation (If they can't get energy from the sun), then the rich will be wiped out also.
This is an immediately existential situation, the only solution to which is to move all energy dependence, including the energy in money, to solar.
As described, your concern would also be addressed by the solution, all nations will have to be aligned with the solution.
Its the end of capitalism, and the beginning of something new - Energyism, and actually the ecosystem of a new superorganism in process of being born.
Its humanity becoming photosynthetic.
Its humanity moving to do what plants do, benefit the planet.
Its humanity moving from net destruction, to net creation.
Its the end of energy slavery for all humans.
Time to party soon :)