I think the article is overplaying the promise of CO reductions.
Around 60% of CO2 (see 1) emissions during cement manufacturing are just a byproduct of the chemical process converting calcium carbonate to lime (see 2) - nothing that solar power can help with.
I thought that the problem with air travel is not (just) the amount of CO2 emitted, but also the altitude, which makes the green house effect bigger per ton of CO2.
It's not about CO2 emissions, but rather the high-altitude NOx that contributes more to climate change than low-altitude emissions. However, it's debatable whether the amount is very significant, at least compared to other sources of NOx.
The byproduct of the chemical process is largely reabsorbed as the cement cures. The part that's from the fuel burned to heat it is not, and that's the part that matters in the long-term balance.