Modern navigation systems, which are found in most of today’s commercial aircraft, are made with low-power circuitry, which is more susceptible to interference than the vacuum-tube circuitry found in older planes.
Conclusion (clearly)
Modern aircraft navigation systems are being put at risk by the electronic devices that passengers carry on board, such as cassette players and laptop computers.
Evidence
Modern navigation systems have low-power circuitry, which is more susceptible to interference than vacuum-tube circuitry found in older planes.
During landing, navigation systems receive radio signals from the airport to guide the plane to the runway.
One plane veered off course during landing and its dials dimmed when a passenger turned on a laptop computer.
Evaluate
We're told that new planes are more vulnerable to interference, but we don't know whether the devices that passengers carry on board actually cause interference.
The only evidence for that idea is this one data point where a dude opened his laptop and the plane seemed to experience interference. Do we know for sure the laptop caused it? Maybe it was a coincidence and the dimming dials and veering off course came from some different cause.
The argument is definitely assuming a causal relationship:
Curious Fact: Why did the plane veer off course / why did the dials dim?
Author's Explanation: The opened laptop caused interference.
To strengthen the argument, we would show more evidence that supports this causal relationship. To weaken it, we would suggest alternative causes of the navigational disruptions or show that the electronic devices are not the source of interference.
Goal
Let's find four answers that help us argue that passenger devices do cause interference for these newer planed.