Don't use tabs, use string formatting.
...
print("{:12}{:12}{:12}{:12}{:12}{:12}{:12}".format(
"VUELO","AEROLINEA","PROCEDENCIA","FECHA","HORA","ESTADO","PUERTA"))
print("{:12}{:12}{:12}{:12}{:12}{:12}{:12}".format(*llegadas))
Change the 12
to the maximum field size for each column, and you're golden.
In fact, though it's less readable:
COLSIZE = 12
# Maybe COLSIZE = max(map(len,llegadas))+1
NUMCOLS = 7
formatstring = "{}{}{}".format("{:",COLSIZE,"}")*NUMCOLS
# {:COLSIZE}*NUMCOLS
headers = ["VUELO","AEROLINEA","PROCEDENCIA","FECHA","HORA","ESTADO","PUERTA"]
print(formatstring.format(*headers))
print(formatstring.format(*llegadas))