'No-fly' pledges like this are really just posturing and/or an attempt to put pressure on the bigger clubs that fly to games often.
If anyone really wanted to reduce the environmental impact of the EFL then the obvious move would be to restructure it into some kind of regional format. At the same time the number of teams in each division could be reduced a little which would impact on player wellbeing and further reduce environmental impact.
For example, the existing 96 teams in the Championship, League 1, League 2 and National League could be joined by 24 other teams from the National Leagues North and South to form 2 sets of 3 x 20 team leagues (north and south). I would have 4 up and 4 down between the regional versions of the Championship, League 1 and League 2 with 2 teams relegated from League 2 and 2 teams promoted from the Championship into the Premier League. 4 teams would be relegated from the Prem with the regional division they go into being based on minimizing the total travel distance (2 teams into north and 2 into south). This would mean that teams in the middle of the country might sometimes go down into the south but sometimes into the north.
I know that this would mean that we would only ever play teams from the southern part of the country but does that really matter in the grand scheme of things?
The biggest issue is that it would necessarily mean that the standard of the regional leagues would be a little lower on average which would make transitions to/from the (national) Premier League more difficult. This could be limited by reducing the number of teams in each league to 18 (so the second tier would be two current Premier League teams, 24 Championship teams and the best 10 League 1 teams).
Based on current league standings (taking just the top 16 League 1 teams) the 20 team Championship North and South would be as follows:
North:
Leicester, Preston, Sunderland, Leeds, Birmingham, Hull, West Brom, Coventry, Middlesbrough, Blackburn, Huddersfield, Stoke, Rotherham, Sheffield Wednesday, Barnsley, Bolton, Derby, Port Vale, Blackpool, Lincoln
South:
Ipswich, Norwich, Cardiff, Southampton, Swansea, Bristol City, Millwall, Argyle, Watford, QPR, Portsmouth, Oxford, Stevenage, Peterborough, Wycombe, Exeter, Charlton, Bristol Rovers, Cambridge, Orient
If there were 18 team leagues then it would be:
North:
Sheffield United, Leicester, Preston, Sunderland, Leeds, Hull, West Brom, Middlesbrough, Blackburn, Huddersfield, Stoke, Rotherham, Sheffield Wednesday, Barnsley, Bolton, Derby, Port Vale, Blackpool
South:
Bournemouth, Ipswich, Birmingham, Norwich, Cardiff, Southampton, Swansea, Coventry, Bristol City, Millwall, Argyle, Watford, QPR, Portsmouth, Oxford, Stevenage, Peterborough, Wycombe
[well... that was a fun way to 'waste' half and hour!]