One might work at opening border in all the years the tunnel is being built - closed borders should't be considered a irreversable thing. Furthermore, of course

One might work at opening border in all the years the tunnel is being built - closed borders should't be considered a irreversable thing. Furthermore, of course there still be flights available. The whole point is to have less flights. So some flights could be shifted to train or boat and for the rest double-checked whether the flight is still needed.