results_set = set()
while True:  # TODO: make the endless loop end
    print len(results_set)
    results = driver.find_elements_by_css_selector("div.flightbox")
    for result in results:
        results_set.add(result)
    print "Results count: %d" % len(results)

    # scroll to the last element
    driver.execute_script("arguments[0].scrollIntoView();", results[-1])

    # wait for more results to load
    wait.until(wait_for_more_than_n_elements((By.CSS_SELECTOR, 'div.flightbox'), len(results)))

RESULT:

0
Results count: 5
5
Results count: 10
10
Results count: 15
15
Results count: 15
15
Results count: 15
15
Results count: 15
15
Results count: 15
15
Results count: 15
15
Results count: 15
15
...
...
..
.
.