An Apple iPhone 4 was glowing red hot and emitted a "significant amount" of dense smoke as it spontaneously combusted on board a flight in Australia in the second reported incident of its kind in the past month.

It's not the first time electronic devices have exploded or caught fire. Numerous incidents have occurred over the past decade including Dell laptops catching fire, a journalist's LG phone catching fire and Sony Australia recalling 4300 laptops (440,000 globally) from its Vaio TZ series due to fears they could overheat, damaging the machines and potentially burning users. In 2009 iPhone users in France also reported similar incidents.

The incident involving a passenger's iPhone 4 glowing red hot occurred on board Regional Express flight ZL319 operating from Lismore to Sydney last Friday after landing, the airline reported.

The second incident, which Fairfax Media was made aware of by an anonymous reader, allegedly happened on November 3 when their iPhone 3GS (an earlier model) did something similar. The reader provided pictures as evidence.

In an emailed statement at 12.35pm today, Apple Australia spokeswoman Fiona Martin said the company was looking "forward to working with officials" investigating the first incident. No comment was offered on the second incident.

In a statement regarding the first incident, Regional Express said a flight attendant carried out "recovery actions" immediately and that the red glow was extinguished successfully, adding that the matter has been reported to the Australian Transport Safety Bureau (ATSB) as well as the Civil Aviation Safety Authority (CASA) for investigation and directions. All passengers and crew on board were unharmed, the airline said.

CASA spokesman Peter Gibson told Fairfax today that the ATSB was going to strip the iPhone 4 down "and try and understand what happened". The intention was "to do that some time this week", he said, adding that the iPhone 4 was no longer operational. Anecdotally he had never heard of a similar incident occurring during or after a flight.

An ATSB spokeswoman said it was very early in their investigation "for anything to happen in regards to the investigation". Its website lists the incident as involving fumes, smoke and fire.

The second incident involved an iPhone 3G model's battery allegedly exploding after a software upgrade.

"My iPhone was expanding in size in terms of its width," the anonymous reader said. "[It] continued to grow in size. Before long the phone refused to even turn on and ... just expanded to what it looks like now."

The reader noted that - like others - their battery life "was rapidly shrinking after updating to the iOS5 .... so much so that it would go completely flat once I got to 30 per cent". Apple acknowledged battery life issues remained after another update.

The reader suspected there was a clear link between their upgrade to the iOS5 software and their battery "exploding".

They said that what was "even worse" was the fact that Apple requested $89 for their iPhone 3GS to be fixed. "I'm the person who lost all their contacts, all my saved university files, all my photos - and now I'm the one whose being asked to fork out the dollars to get it fixed. Are you kidding me?"

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