Я обнаружил, что забыл добавить небольшую часть кода, чтобы он заработал.
Итак, вот мое решение:
import xml.etree.ElementTree as ET
import requests
atc = ["ADR_CTR", "ADR_W_CTR", "ADR_U_CTR", "ADR_E_CTR", "LDZO_CTR", "LJLA_CTR", "LYBA_CTR", "LWSS_CTR", "LAAA_CTR", "LQSB_CTR", "LJLJ_TWR", "LJLJ_APP", "LJLJ_GND", "LJMB_TWR", "LJMB_APP", "LJPZ_TWR", "LJPZ_APP", "LDZA_APP", "LDZA_TWR", "LDZA_GND", "LDDU_TWR", "LDDU_APP", "LDSP_TWR", "LDSP_APP", "LDPL_TWR", "LDPL_APP", "LDRI_TWR", "LDZD_TWR", "LDZD_APP", "LDOS_TWR", "LDOS_APP", "LYBE_APP",
"LYBE_TWR", "LYBE_GND", "LYTV_TWR", "LYPG_TWR", "LYPG_APP", "LYNI_TWR", "LYNI_APP", "LATI_APP", "LATI_TWR", "LATI_GND", "LWSK_TWR", "LWSK_APP", "LWSK_GND", "LWOH_TWR", "BKPR_TWR", "BKPR_APP", "LQSA_TWR", "LQSA_GND", "LQSA_APP", "LQMO_TWR", "LQMO_APP", "LQBK_TWR", "LQBK_APP", "LQTZ_TWR", "LQTZ_APP", "LYUZ_TWR", "LYUZ_APP", "LYKV_APP", "LYKV_TWR", "LDZO_T_CTR", "LJLA_T_CTR", "LYBA_T_CTR",
"LWSS_T_CTR", "LAAA_T_CTR", "LQSB_T_CTR", "LJLJ_T_TWR", "LJLJ_T_APP", "LJLJ_T_GND", "LJMB_T_TWR", "LJMB_T_APP", "LJPZ_T_TWR", "LJPZ_T_APP", "LDZA_T_APP", "LDZA_T_TWR", "LDZA_T_GND", "LDDU_T_TWR", "LDDU_T_APP", "LDSP_T_TWR", "LDSP_T_APP", "LDPL_T_TWR", "LDPL_T_APP", "LDRI_T_TWR", "LDZD_T_TWR", "LDZD_T_APP", "LDOS_T_TWR", "LDOS_T_APP", "LYBE_T_APP",
"LYBE_T_TWR", "LYBE_T_GND", "LYTV_T_TWR", "LYPG_T_TWR", "LYPG_T_APP", "LYNI_T_TWR", "LYNI_T_APP", "LATI_T_APP", "LATI_T_TWR", "LATI_T_GND", "LWSK_T_TWR", "LWSK_T_APP", "LWSK_T_GND", "LWOH_T_TWR", "BKPR_T_TWR", "BKPR_T_APP", "LQSA_T_TWR", "LQSA_T_GND", "LQSA_T_APP", "LQMO_T_TWR", "LQMO_T_APP", "LQBK_T_TWR", "LQBK_T_APP", "LQTZ_T_TWR", "LQTZ_T_APP", "LYUZ_T_TWR", "LYUZ_T_APP", "LYKV_T_APP", "LYKV_T_TWR"]
tree = ET.fromstring(requests.get('http://vatbook.euroutepro.com/xml2.php?fir=').text)
#Testing what is displayed
for atcs in tree.find('atcs'):
callsign = atcs.find('callsign')
name = atcs.find('name')
time_start = atcs.find('time_start')
time_end = atcs.find('time_end')
if callsign is not None:
print(f"{name.text} booked {callsign.text} from {time_start.text} to {time_end.text}")