The thinning of the ozone layer can be reduced by the controlled use of 
 

The ozone layer can be reduced by the controlled use of refrigerants and high-flying jets.

The nitrous oxides released by high-altitude supersonic aircraft flying in the stratospheric zone are very reactive and can damage a large amount of ozone. 
Refrigerants are chemical compounds used in cooling systems like refrigerators, air conditioning, etc. They contain aerosols that release chlorofluorocarbons which have the tendency to split ozone and cause thinning of ozone layer.