Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| City | Country | IATA | ICAO | Airport |
| --- | --- | --- | --- | --- |
| Adana | Turkey | ADA | LTAF | Adana Şakirpaşa Airport |
| Antalya | Turkey | AYT | LTAI | Antalya Airport |
| Bodrum | Turkey | BJV | LTFE | Milas-Bodrum Airport |
| Dalaman | Turkey | DLM | LTBS | Dalaman Airport |
| Erbil | Iraq | EBL | ORER | Erbil International Airport |
| Gaziantep | Turkey | GZT | LTAJ | Oğuzeli Airport |
| Istanbul | Turkey | IST | LTBA | Atatürk International Airport (base) |
| Istanbul | Turkey | SAW | LTFJ | Sabiha Gökçen International Airport |
| İzmir | Turkey | ADB | LTBJ | Adnan Menderes Airport |
| Kars | Turkey | KSY | LTCF | Kars Airport |
| Kayseri | Turkey | ASR | LTAU | Erkilet International Airport |
| North Nicosia | Northern Cyprus | ECN | LCEN | Ercan International Airport |
| Simferopol | Ukraine | SIP | UKFF | Simferopol International Airport |
| Sulaymaniah | Iraq | ISU | ORSU | Sulaimaniyah International Airport |
| Tehran | Iran | IKA | OIIE | Imam Khomeini International Airport |
| Tbilisi | Georgia | TBS | UGTB | Tbilisi International Airport |
| Van | Turkey | VAN | LTCI | Van Ferit Melen Airport |
| Yerevan | Armenia | EVN | UDYZ | Zvartnots International Airport |
Question:
What is the ICAO when the IATA is ist?
Answer:
LTBA