A Greek national flag flies above tourists on Acropolis Hill in Athens on  July 8. (Yorgos Karahalis/Bloomberg)

Greece's economic crisis is an extremely unusual event with serious implications for the rest of Europe. But the crisis is already making itself known in Greece and outside it, with some unusual knock-on effects.

Here are nine unexpected effects the crisis has had so far:

1. Some pilots carry $11,200 in cash to ensure that they don't run out of money in Greece and have to abandon their planes on the runway

Edelweiss airline in Switzerland has taken unusual precautions for its flights to Greece: They carry more fuel in their tanks, and pilots are equipped with up to $11,200 in cash. Usually, airlines pay by invoice, but given the uncertainties of the Greek crisis, cash is the better option to pay for fuel and landing charges.

Speaking to Switzerland's Blick newspaper, a spokesperson for the company confirmed that pilots were tasked to prepare for a worst-case scenario. "We usually do not carry that much money on our planes," Andreas Meier said.

[In Greece, Chanel becomes more valuable than cash]

2. Greeks are practically unable to book flights out of the country

An abandoned passenger terminal stands astride empty runways at the site of the former Ellinikon International Airport in Athens on June 25. (Simon Dawson/Bloomberg)

At least 35 airlines have said that they do not accept Greek credit cards anymore. Hence, Greeks will either have to pay in cash (which isn't even a possibility with some airlines), or will have to use a foreign credit card. Moreover, many airlines have stopped selling tickets through Greek travel agents.

3. Greek truck drivers are stranded elsewhere in Europe because their bank accounts have been frozen

Greek tourists and workers abroad face similar problems: Given that their credit cards were blocked, many of them cannot return home. According to German media reports, hundreds of Greek truck drivers are stranded at petrol stations throughout Europe, unable to pay for fuel with their blocked cards.

[How one weeping man put a face on Greece’s debt crisis]

4. Refugees on Greek islands are running out of food and water because the country's government is unable to help

The Kos police station courtyard overflows with new arrivals awaiting paperwork to travel to Athens. (Charles Ommanney/The Washington Post)

Even more vulnerable are the thousands of refugees who are seeking asylum on one of the country's many islands. Due to a shortage of water and food, Greek authorities fear that conditions in migrant centers could lead to unrest and a humanitarian crisis, according to German news agency dpa.

"The programs for food supply have been stopped. Revolts could happen," Tasia Christofilopoulou, the deputy Greek minister for migration, was quoted as saying in parliament by dpa.

5. Other European countries and NGOs are preparing humanitarian aid for Greece

“Of course we do not want to abandon the Greeks, but they do not have to be a member of the euro zone in order to receive help,” Christian von Stetten, a lawmaker from German Chancellor Angela Merkel’s Christian Democratic Union, said recently, summing up the mood in Berlin.

The E.U. is preparing humanitarian aid in case Greece leaves the eurozone. Critics, however, say that humanitarian aid would be a cheap alternative to a costly bailout program.

[Germany has defaulted on its debts, too]

6. Imported goods are piling up at seaports because nobody can pay for them

More than 60 percent of all goods consumed in Greece are imports. Due to limitations on cash withdrawals and capital controls, most of those imports have been stored for days now as Greek traders were unable to pay for the goods, according to the New York Times. "Food, some medicines and other daily necessities are beginning to pile up on the docks at Piraeus, the international seaport outside Athens," the paper said. In the long term, this could lead to even more serious food shortages.

7. More Greeks are applying for passports. Local newspapers say that most of them want to leave the country in the case of a Grexit

Greek newspaper Kathimerini reported that more than 1,500 people apply for passports every day in Athens alone. Passport applications have increased by 50 percent compared to last year, according to Germany's Stern magazine.

8. Fewer tourists are traveling to Greece, which will make the country's economic situation even worse

A tourist holds an umbrella to protect from the sun as she visits the Temple of Zeus in Athens on July 7. (Spyros Tsakiris/AP)

Since a referendum was announced about 1.5 weeks ago, tourism bookings have decreased by 30 percent, according to German news channels n-tv and N24.

9. In Athens, the political debate is transforming city walls

Graffiti with political messages have appeared all over Athens. Using the E.U. logo, the German word nein (which means no) is being displayed on this graffiti in the Greek capital:

The German word "nein" (no) on graffiti displaying the European Union  flag and a euro symbol on July 8 in Athens. (Christopher Furlong/Getty Images)

Some blame German Chancellor Angela Merkel for Greece's default. Tensions have run high for years, but in recent weeks, the anger has been increasingly visible on Greek streets.

A sign outside the Bank of Greece is defaced with graffiti to read "Banque de Merkel" on July 6 in Athens.  (Christopher Furlong/Getty Images)

The photo below was taken in central Athens and shows a young woman walking past a graffiti reading "Death of Euro" and which was composed by French street artist Goin.

(Aris Messinis/AFP via Getty Images)