Requires two python dependencies: `beautifulsoup4` and `requests` (installable through pip)

distance.py

import sys

from bs4 import BeautifulSoup
import requests


url = ("http://www.webflyer.com/travel/mileage_calculator/getmileage.php?city="
       "%s&city=%s&city=&city=&city=&city=&bonus=0&bonus_use_min=0&class_bonus"
       "=0&class_bonus_use_min=0&promo_bonus=0&promo_bonus_use_min=0&min=0&min"
       "_type=m&ticket_price=")

def get_distance(airport1, airport2):
    r = requests.get(url % (airport1, airport2))
    # BeautifulSoup doesn't like underscores in class names
    content = r.content.replace('row_odd_font', 'rowoddfont')
    soup = BeautifulSoup(content)
    spans = soup.find_all('span', attrs={'class': 'rowoddfont'})
    span = spans[1]
    text = span.text.split(' ')
    num_miles = text[0]
    return num_miles

if len(sys.argv) < 3:
    print "python distance.py {AIRPORT1} {AIRPORT2}"
else:
    print get_distance(sys.argv[1], sys.argv[2])