As FunkyMonk has remarked, the format of your input file (primarily space-separated) doesn't match the way you split each line into fields (split on ";"), so it is not surprising that some of the fields come out undefined.

Moreover, you say:

Here is my output file

 
            DAL11    527    530     3
            
ACA87    531    533     2
            
SHT8K    528    535     7
            
DLH9F    533    537     4
[download]

...but the typical print statement in your program is

print OUTFILE "$aircraft_id;$ATO_min;$CTO_min $delay_ATO_CTO_m";
[download]

That would print a semicolon-separated output, not the space-separated one you present. You need to reconcile your separators.

Anno

Comment on Re: warnings unexpecetd Select or Download Code