Complex sentence: Eventually Douglas C-1 transports were modified to carry up to 9 litter patients and were used on an opportune basis in the US and Panama, this lead to a directive that all future military transports be equipped with brackets for carrying litters.
Split into simpler sentences: Eventually Douglas C-1 transports were modified to carry up to 9 litter patients and were used on an opportune basis in the US and Panama. This led to a directive that all future military transports be equipped with brackets for carrying litters.