A TGV Duplex carries 510 passengers at 300km/h. For instance the TGV line going to south east France carries 75000 passengers per day with a theoretical capacity at 350000 passengers per day. I let you convert that into airplanes ;)
Air France domestic backbone is home-grown a320s. Standard layout in their use of those is 174 pax.
TGV Sud-Est is 350000 / 174 ~= 2012 flights per day.
There's no airport in the world that handles traffic like that. ATL comes close at 1970 flights daily, but this 2012 is only the capacity on TGV Sud-Est. This doesn't count any of the other lines, of which there are many: https://en.wikipedia.org/wiki/List_of_TGV_services
Not only is train much better at handling large amount of capacity, it do so with a lower carbon footprint. Looking at the transportation sector in EU-27:
"Within the transport sector, aviation was responsible for 13.2 % of GHG emissions(144.3 megatonnes CO2 equivalent (Mt CO2e) and rail for 0.4 % (4.3 Mt CO2e). The latter refers to the emissions by diesel trains only. This compares with a share of 71.8 % for road transport and a share of 14.1 % for navigation
(EC, 2020b)" (EEA Report No 19/2020)
There is a good reason why trains are commonly used between mines and ports. A single train can have around 70-100 of cars, each loaded with 100 tons of Ore. To do the same with planes would be impossible expensive and the emissions would be insane.
The only thing that can get near in terms of capacity and emissions are boats, although that sector is in large need of modernization. They discussed this in an other article about France, since they got several large rivers that could see increased utilization by the transportation sector.
Obviously in both cases, transportation will take longer. I would assume that some delivery services will be exempted when a slower transportation is not suitable.