Updated with Turkish official quoted by Reuters in fifth paragraphTurkish President Recep Tayyip Erdoğan said he aimed to quadruple trade and form closer links with Russia during a joint press conference with his Russian counterpart Vladimir Putin at an aviation show in Moscow on Tuesday.The Turkish president's trip to Russia's MAKS-2019 air show was announced last week, one of the main backers of Syrian President Bashar Assad.Turkish troops at an observation point in Idlib, the last rebel-held province in Syria, were cut off as Assad regime forces advanced last week. A military convoy sent by Turkey to support Turkish-backed rebels in the province was targeted in an air strike, triggering speculation that Russia was involved in the attack.Idlib was on the agenda for the presidents' bilateral talks, Moscow spokesman Dimitry Peskov told reporters on Monday. A Turkish official told Reuters on Tuesday that the security of Turkish soldiers would be a "key topic" in the meeting.But there was no discussion of the Syrian situation during the press conference, with Erdoğan instead discussing his desire to develop closer ties with Russia.Turkey is seeking alternatives for the new generation F-35 fighter jet after being expelled from the programme for its S-400 purchase. So, the moment at the air show when Putin showed Erdoğan the cockpit of the Russian Su-57 fighter jet drew considerable attention.Russian state-funded news outlet Sputnik Türkiye published a lighthearted exchange caught on film while the two presidents examined the fighter jet."Is this the Su-57? Can it fly?" Erdoğan asked Putin, who responded that they would be flying at the the air show."Are we going to buy some of these?" Erdoğan quipped. "You can if you want", Putin replied, drawing laughter.A deal to sell Turkey the new generation fighters would be a boon for Russia, which began the delivery of a second battery of S-400 systems to Turkey this week, Turkish Defence Minister Hulusi Akar said on Monday As the new shipments began to arrive near Ankara, Erdoğan told the crowd near the Russian capital that the links the two countries had been making in aviation and space technologies would help deepen bilateral ties.The Turkish president said this could lead to an increase in the already impressive number of Russian tourists visiting Turkey, with 6 million coming to the country this year.It could also help Turkey meet its target of $100 billion in trade volume, Erdoğan said. This figure is the same as the target discussed by Erdoğan and U.S. President Donald Trump this year, and is nearly four times the current amount of bilateral trade with Russia.