import re

txt =  'Port of Discharge/ Airport of destination\tXYZABC\t\t\t\t\t\t\t\t44B'
pat = r' port.{0,6}discharge.{0,3}/.{0,3}airport.{0,7}destination(?=.*44B)'
reg_ind = [(m.start(0),m.end(0)) for m in re.finditer(pat, txt,re.IGNORECASE | re.VERBOSE)]
print(reg_ind)